ksh(1) ksh(1)NAME ksh - run the Korn shell, a command interpreter compatible with Bourne shell SYNOPSIS ksh [-a] [-e] [-f] [-h] [-i] [-k] [-m] [-n] [-o] [-p] [-r] [-s] [-t] [-u] [-v] [-x] [-o option]... [-c string] [arg...] DESCRIPTION ksh is a command programming language that executes commands that are read from a terminal or a file. See ``Invocation'' later in this section for the meaning of arguments to the shell. Definitions A metacharacter is one of the following characters: ; & ( ) | < > newline space tab A blank is a tab or a space. An identifier is a sequence of letters, digits, or underscores starting with a letter or underscore. Identifiers are used as names for aliases, functions, and named parameters. A word is a sequence of characters separated by one or more nonquoted metacharac- ters. Commands A simple-command is a sequence of blank-separated words which may be preceded by a parameter assignment list (see ``Environment'' later in this section). The first word specifies the command name to be executed. With exceptions described later, the remaining words are passed as arguments to the invoked command. The command name is passed as argu- ment 0 (see exec(2)). The value of a simple-command is its exit status if it terminates normally, or (octal) 200+status if it terminates abnormally (see signal(3) for a list of status values). A pipeline is a sequence of one or more commands separated by a vertical bar (|). The standard output of all but the last command is connected by a pipe(2) to the standard input of the next command. Each command is run as a separate pro- cess; the shell waits for the final command to terminate. The exit status of a pipeline is the exit status of the last command. A list is a sequence of one or more pipelines separated by ;, &, &&, or ||, and optionally terminated by ;, &, or |&. Of these five symbols, ;, &, and |& have equal precedence, which is lower than that of && and ||. The symbols && and || also have equal precedence. A semicolon (;) causes April, 1990 1
ksh(1) ksh(1)sequential execution of the preceding pipeline; an ampersand (&) causes asynchronous execution of the preceding pipeline (that is, the shell does not wait for that pipeline to fin- ish). The symbol |& causes asynchronous execution of the preceding command or pipeline with a two-way pipe esta- blished to the parent shell. The standard input and output of the spawned command can be written to and read from by the parent shell using the -p flag option of the special commands, read and print described later. Only one such command can be active at any given time. The symbol && (||) causes the list following it to be executed only if the preceding pipeline returns a zero (nonzero) value. An arbi- trary number of newlines may appear in a list, instead of semicolons, to delimit commands. Unless stated otherwise, the value returned is that of the last simple-command executed in the command. A command is either a simple-command or one of the following: for identifier [in word ...] do list done Each time a for command is executed, identifier is set to the next word taken from the in word list. If in word ... is omitted, then the for command executes the do list once for each positional parameter that is set (see ``Parameter Substitution'' later). Execution ends when there are no more words in the list. select identifier [in word ... ] do list done A select command prints on standard error (file descriptor 2), the set of words, each preceded by a number. If in word ... is omitted, then the position- al parameters are used instead (see ``Parameter Substi- tution'' later). The PS3 prompt is printed and a line is read from the standard input. If this line consists of the number of one of the listed words, then the value of the parameter identifier is set to the word corresponding to this number. If this line is empty, the selection list is printed again. Otherwise the value of the parameter identifier is set to null. The contents of the line read from standard input is saved in the parameter REPLY. The list is executed for each selection until a break or end-of-file is encountered. case word in [pattern [ | pattern] ... ) list ;; ] ... esac A case command executes the list associated with the first pattern that matches word. The form of the pat- terns is the same as that used for filename generation (see ``Filename Generation'' later). if list then list [elif list then list] ... [else list] fi The list following if is executed and, if a zero exit status is returned, the list following the first then 2 April, 1990
ksh(1) ksh(1)is executed. Otherwise, the list following elif is ex- ecuted and, if its value is zero, the list following the next then is executed. Failing that, the else list is executed. If no else list or then list is executed, then the if command returns a zero exit status. while list do list done until list do list done A while command repeatedly executes the while list and, if the exit status of the last command in the list is zero, executes the do list; otherwise the loop ter- minates. If no commands in the do list are executed, then the while command returns a zero exit status; un- til may be used in place of while to negate the loop termination test. (list) Executes list in a separate environment. Note that if two adjacent open parentheses are needed for nesting, a space must be inserted to avoid arithmetic evaluation as described later. A parenthesized list used as a command argument, denoting ``process substitution,'' is also described. {list;} list is simply executed. Note that { is a keyword and requires a blank in order to be recognized. function identifier {list;} identifier () {list;} Defines a function which is referenced by identifier. The body of the function is the list of commands between { and }. (See ``Functions'' later in this sec- tion). time pipeline The pipeline is executed and the elapsed time, as well as the user and system time, are printed on standard error. The following keywords are recognized only when occurring as the first word of a command and when not quoted. if then else elif fi case esac for do while until done { } function select time Comments A word beginning with a # causes that word and all the fol- lowing characters prior to a newline to be ignored. April, 1990 3
ksh(1) ksh(1)Aliasing The first word of each command is replaced by the text of an alias if an alias for this word has been defined. The first character of an alias name can be any nonspecial printable character, but the rest of the characters must be the same as for a valid identifier. The replacement string can con- tain any valid shell script, including the metacharacters listed earlier. The first word of each command of the re- placed text will not be tested for additional aliases. If the last character of the alias value is a blank, then the word following the alias will also be checked for alias sub- stitution. Aliases can be used to redefine special built-in commands but cannot be used to redefine the keywords listed earlier. Aliases can be created, listed, and exported with the alias command and can be removed with the unalias com- mand. Exported aliases remain in effect for subshells but must be reinitialized for separate invocations of the shell (see ``Invocation'' later in this section). Aliasing is performed when scripts are read, not while they are executed. Therefore, for an alias to take effect, the alias command has to be executed before the command which references the alias is read. Aliases are frequently used as a type of shorthand for full pathnames. A flag option to the aliasing facility allows the value of the alias to be automatically set to the full pathname of the corresponding command. These aliases are called ``tracked'' aliases. The value of a tracked alias is defined the first time the corresponding command is looked up and becomes undefined each time the PATH variable is reset. These aliases remain tracked so that the next subse- quent reference will redefine the value. Several tracked aliases are compiled into the shell. The -h flag option of the set command makes each command name that is a valid alias name into a tracked alias. The following ``exported aliases'' are compiled into the shell but can be unset or redefined: false='let 0' functions='typeset -f' history='fc -l' integer='typeset -i' nohup='nohup ' r='fc -e -' true=':' type='whence -v' hash='alias -t' 4 April, 1990
ksh(1) ksh(1)Tilde Substitution After alias substitution is performed, each word is checked to see if it begins with an unquoted tilde (~). If it does, then the word prior to a / is checked to see if it matches a user name in the /etc/passwd file. If a match is found, the ~ and the matched login name is replaced by the login direc- tory of the matched user. This is called a tilde substitu- tion. If no match is found, the original text is left un- changed. A ~ by itself, or in front of a /, is replaced by the value of the HOME parameter. A ~ followed by a + or - is replaced by the value of the parameter PWD and OLDPWD respectively. In addition, the value of each keyword parameter is checked to see if it begins with a ~ or if a ~ appears after a :. In either of these cases, a tilde substitution is attempted. Command Substitution The standard output from a command enclosed in parentheses preceded by a dollar sign $() or a pair of grave accents `` may be used as part or all of a word; trailing newlines are removed. In the second (archaic) form, the string between the quotes is processed for special quoting characters be- fore the command is executed. (See ``Quoting'' later.) The command substitution $(cat file) can be replaced by the equivalent but faster $(<file). Command substitution of most special commands that do not perform input/output redirection are carried out without creating a separate pro- cess. Process Substitution This feature is only available on versions of the A/UX operating system that support the /dev/fd directory for nam- ing open files. Each command argument of the form (list), <(list), or >(list) will run the process list asynchronously connected to some file in /dev/fd. The name of this file will become the argument to the command. If the form with > is selected then writing on this file will provide input for list. If < is used or omitted, then the file passed as an argument will contain the output of the list process. For example, paste (cut -f1 file1) (cut -fC file2) | tee >(proc1)>(proc2) cuts fields 1 and 3 from the files file1 and file2 respec- tively, pastes the results together, and sends it to pro- cess1 and process2, as well as putting it onto the standard output. Note that the file, which is passed as an argument to the command, is an A/UX pipe(2) so programs that expect to lseek(2) on the file will not work. April, 1990 5
ksh(1) ksh(1)Parameter Substitution A parameter is an identifier, one or more digits, or any of the characters *, @, #, ?, -, $, and !. A named parameter (a parameter denoted by an identifier) has a value and has zero or more attributes. By using the typeset special com- mand, named parameters can be assigned values and attri- butes. The attributes supported by the shell are described later with the typeset special command. Exported parameters pass values and attributes to subshells but values only to the environment. The shell supports a limited one-dimensional array facility. An element of an array parameter is referenced by a sub- script. A subscript is denoted by a [, followed by an ar- ithmetic expression (see ``Arithmetic Evaluation'' later in this section), followed by a ]. The value of all subscripts must be in the range of 0 through 511. Arrays need not be declared. Any reference to a named parameter with a valid subscript is legal and an array will be created if neces- sary. Referencing an array without a subscript is equivalent to referencing the first element. The value of a named parameter may also be assigned by writ- ing: name=value [ name=value ] ... If the integer attribute, -i, is set for name the value is subject to arithmetic evaluation as described later. Positional parameters denoted by a number are assigned values with the set special command. Parameter $0 is set from argument zero when the shell is invoked. The character $ is used to introduce substitutable parame- ters. ${parameter} The value, if any, of the parameter is substituted. The braces are required when parameter is followed by a letter, digit, or underscore that is not to be inter- preted as part of its name or when a named parameter is subscripted. If parameter is one or more digits, then it is a positional parameter. A positional parameter of more than one digit must be enclosed in braces. If parameter is * or @, then all the positional parame- ters, starting with $1, are substituted (separated by a field separator character). If an array identifier with subscript * or @ is used, then the value for each of the elements is substituted (separated by a field separator character). 6 April, 1990
ksh(1) ksh(1)${#parameter} If parameter is * or @, the number of positional param- eters is substituted. Otherwise, the length of the value of the parameter is substituted. ${#identifier[*]} The number of elements in the array identifier is sub- stituted. ${parameter:-word} If parameter is set and is not null, then substitute its value; otherwise substitute word. ${parameter:=word} If parameter is not set or is null, then set it to word; the value of the parameter is then substituted. Positional parameters may not be assigned in this way. ${parameter:?word} If parameter is set and is not null, then substitute its value; otherwise print word and exit from the shell. If word is omitted then a standard message is printed. ${parameter:+word} If parameter is set and is not null, then substitute word; otherwise substitute nothing. ${parameter#pattern} ${parameter##pattern} If the shell pattern matches the beginning of the value of parameter, then the value of this substitution is the value of the parameter with the matched portion deleted; otherwise the value of this parameter is sub- stituted. In the first form, the smallest matching pattern is deleted and in the latter form, the largest matching pattern is deleted. ${parameter%pattern} ${parameter%%pattern} If the shell pattern matches the end of the value of parameter, then the value of this substitution is the value of parameter with the matched part deleted; oth- erwise substitute the value of parameter. In the first form, the smallest matching pattern is deleted and in the latter form, the largest matching pattern is delet- ed. In the preceding, word is not evaluated unless it is to be used as the substituted string, so that, in the following example, pwd is executed only if d is not set or is null. April, 1990 7
ksh(1) ksh(1)echo ${d:- $(pwd)} If the colon (:) is omitted from the above expression, then the shell only checks as to whether parameter is set or not. The following parameters are automatically set by the shell. # The number of positional parameters in decimal. - Flags supplied to the shell on invocation or by the set command. ? The decimal value returned by the last executed command. $ The process number of this shell. _ The last argument of the previous command. This parameter is not set for commands which are asyn- chronous. This parameter is also used to hold the name of the matching MAIL file when checking for mail. Finally, the value of this parameter is set to the full pathname of each program the shell in- vokes and is passed in the environment. ! The process number of the last background command invoked. PPID The process number of the parent of the shell. PWD The present working directory set by the cd com- mand. OLDPWD The previous working directory set by the cd com- mand. RANDOM Each time this parameter is referenced, a random integer is generated. The sequence of random numbers can be initialized by assigning a numeric value to RANDOM. REPLY This parameter is set by the select statement and by the read special command when no arguments are supplied. SECONDS Each time this parameter is referenced, the number of seconds since shell invocation is returned. If this parameter is assigned a value, then the value returned upon reference will be the value that was assigned plus the number of seconds since the as- signment. 8 April, 1990
ksh(1) ksh(1)The following parameters are used by the shell. CDPATH The search path for the cd command. COLUMNS If this variable is set, the value is used to de- fine the width of the edit window for the shell edit modes and for printing select lists. EDITOR If the value of this variable ends in vi and the VISUAL variable is not set, then the corresponding flag option (see ``Special Commands'') will be turned on. ENV If this parameter is set, then parameter substitu- tion is performed on the value to generate the pathname of the script that will be executed when the shell is invoked (see ``Invocation''). This file is typically used for alias and function de- finitions. FCEDIT The default editor name for the fc command. IFS Internal field separators, normally space, tab, and newline that are used to separate command words which result from command or parameter sub- stitution and for separating words with the spe- cial command read. The first character of the IFS parameter is used to separate arguments for the $* substitution (see ``Quoting''). HISTFILE If this parameter is set when the shell is in- voked, then the value is the pathname of the file that will be used to store the command history (see ``Command Re-entry''). HISTSIZE If this parameter is set when the shell is in- voked, then the number of previously entered com- mands that are accessible by this shell will be greater than or equal to this number. The default is 128. HOME The default argument (home directory) for the cd command. LINES If this variable is set, the value is used to determine the column length for printing select lists. Select lists will print vertically until about two-thirds of LINES lines are filled. MAIL If this parameter is set to the name of a mail file and the MAILPATH parameter is not set, then the shell informs the user of arrival of mail in April, 1990 9
ksh(1) ksh(1)the specified file. MAILCHECK This variable specifies how often (in seconds) the shell will check for changes in the modification time of any of the files specified by the MAILPATH or MAIL parameters. The default value is 600 seconds. When the time has elapsed, the shell will check before issuing the next prompt. MAILPATH A colon (:) separated list of filenames. If this parameter is set, then the shell informs the user of any modifications to the specified files that have occurred within the last MAILCHECK seconds. Each filename can be followed by a ? and a message that will be printed. The message will undergo parameter and command substitution with the param- eter, $_, defined as the name of the file that has changed. The default message is You have mail in $_. PATH The search path for commands (see ``Execution''). PS1 The value of this parameter is expanded for param- eter substitution to define the primary prompt string which by default is $. The character ! in the primary prompt string is replaced by the com- mand number (see ``Command Re-entry''). PS2 Secondary prompt string, by default >. PS3 Selection prompt string used within a select loop, by default #?. SHELL The pathname of the shell is kept in the environ- ment. At invocation, if the value of this vari- able contains an r in the basename, then the shell becomes restricted. TMOUT If set to a value greater than zero, the shell will terminate if a command is not entered within the prescribed number of seconds after issuing the PS1 prompt. (Note that the shell can be compiled with a maximum bound for this value which cannot be exceeded.) VISUAL If the value of this variable ends in vi then the corresponding option (see ``Special Commands'') will be turned on. The shell gives default values to PATH, PS1, PS2, MAILCHECK, TMOUT, and IFS, while HOME, SHELL, ENV, and MAIL are not set by the shell (although HOME is set by login(1)). On some 10 April, 1990
ksh(1) ksh(1)systems MAIL and SHELL are also set by login(1)). Blank Interpretation After parameter and command substitution, the results of substitutions are scanned for the field separator characters (those found in IFS) and split into distinct arguments where such characters are found. Explicit null arguments "" or '' are retained. Implicit null arguments (those resulting from parameters that have no values) are removed. Filename Generation Following substitution, each command word is scanned for the characters *, ?, and [ unless the -f option has been set. If one of these characters appears, then the word is regard- ed as a pattern. The word is replaced with alphabetically sorted filenames that match the pattern. If no filename is found that matches the pattern, then the word is left un- changed. When a pattern is used for filename generation, the character . at the start of a filename or immediately following a /, as well as the / itself, must be matched ex- plicitly. In other instances of pattern matching the / and . are not treated specially. * Matches any string, including the null string. ? Matches any single character. [...] Matches any one of the enclosed characters. A pair of characters separated by - matches any character lexically between the pair, inclusive. If the first character following the opening [ is a ! then any character not enclosed is matched. A - can be in- cluded in the character set by putting it as the first or last character. Quoting Each of the metacharacters listed above (see ``Definitions'' earlier) has a special meaning to the shell and causes ter- mination of a word unless quoted. A character may be ``quoted'' (that is, made to stand for itself) by preceding it with a backslash (\). The pair \newline is ignored. All characters enclosed between a pair of single quote marks '' are quoted. A single quote cannot appear within single quotes. Inside double quote marks "" parameter and command substitution occurs and \ quotes the characters \, `, ", and $. The meaning of $* and $@ is identical when not quoted or when used as a parameter assignment value or as a filename. However, when used as a command argument, $* is equivalent to $1d $2d..., where d is the first character of the IFS parameter, whereas $@ is equivalent to $1 $2.... Inside grave accent marks (``), \ quotes the characters \, `, and $. If the grave accents occur within double quotes, then \ April, 1990 11
ksh(1) ksh(1)also quotes the character ". The special meaning of keywords or aliases can be removed by quoting any character of the keyword. The recognition of function names or special command names listed later in this section cannot be altered by quoting them. Arithmetic Evaluation An ability to perform integer arithmetic is provided with the special command let. Evaluations are performed using long arithmetic. Constants are of the form [base#]n where base is a decimal number between 2 and 36 representing the arithmetic base and n is a number in that base. If base is omitted, then base 10 is used. An internal integer representation of a named parameter can be specified with the -i option of the typeset special com- mand. When this attribute is selected, the first assignment to the parameter determines the arithmetic base to be used when parameter substitution occurs. Since many of the arithmetic operators require quoting, an alternative form of the let command is provided. For any command which begins with a ((, all the characters until a matching )) are treated as a quoted expression. More pre- cisely, ((...)) is equivalent to let "...". Prompting When used interactively, the shell prompts with the value of PS1 before reading a command. If at any time a newline is typed and further input is needed to complete a command, then the secondary prompt (that is, the value of PS2) is is- sued. Input/Output Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell. The following may appear anywhere in a simple- command or may precede or follow a command and are not passed on to the invoked command. Command and parameter substitution occurs before word or digit is used except as noted. Filename generation occurs only if the pattern matches a single file and blank interpretation is not per- formed. <word Use file word as standard input (file descrip- tor 0). >word Use file word as standard output (file descriptor 1). If the file does not exist then it is created; otherwise, it is truncated to zero length. 12 April, 1990
ksh(1) ksh(1)>>word Use file word as standard output. If the file exists then output is appended to it (by first seeking to the end-of-file); otherwise, the file is created. <<[-]word The shell input is read up to a line that is the same as word, or to an end-of-file. No parameter substitution, command substitution, or filename generation is performed on word. The resulting document, called a ``here- document,'' becomes the standard input. If any character of word is quoted, then no in- terpretation is placed upon the characters of the document; otherwise, parameter and command substitution occurs, the \newline command is ignored, and \ must be used to quote the char- acters \, $, `, and the first character of word. If - is appended to <<, then all lead- ing tabs are stripped from word and from the document. <&digit The standard input is duplicated from the file descriptor digit (see dup(2)). Similarly for the standard output using >& digit. <&- The standard input is closed. Similarly for the standard output using >&-. If one of the above is preceded by a digit, then the file descriptor number referred to is that specified by the digit (instead of the default 0 or 1). For example, ...2>&1 means file descriptor 2 is to be opened for writing as a du- plicate of file descriptor 1. The order in which redirections are specified is signifi- cant. The shell evaluates each redirection in terms of the (file descriptor, file) association at the time of evalua- tion. For example, ...1>fname2>&1 first associates file descriptor 1 with file fname. It then associates file descriptor 2 with the file associated with file descriptor 1 (that is, fname). If the order of redirections were reversed, file descriptor 2 would be asso- ciated with the terminal (assuming previous association by file descriptor 1) and then file descriptor 1 would be asso- ciated with file fname. April, 1990 13
ksh(1) ksh(1)If a command is followed by & and job control is not active, then the default standard input for the command is the empty file /dev/null. Otherwise, the environment for the execu- tion of a command contains the file descriptors of the in- voking shell as modified by input/output specifications. Environment The environment (see environ(7)) is a list of name-value pairs that is passed to an executed program in the same way as a normal argument list. The names must be identifiers and the values are character strings. The shell interacts with the environment in several ways. On invocation, the shell scans the environment and creates a parameter for each name found, giving it the corresponding value and marking it export. Executed commands inherit the environment. If the user modifies the values of these parameters or creates new ones, using the export or typeset -x commands, they become part of the environment. The environment seen by any exe- cuted command is thus composed of any name-value pairs ori- ginally inherited by the shell, whose values may be modified by the current shell, plus any additions which must be noted in export or typeset -x commands. The environment for any simple-command or function may be augmented by prefixing it with one or more parameter assign- ments. A parameter assignment argument is a word of the form identifier=value. Thus, the following two commands are equivalent (as far as the above execution of cmd is con- cerned). TERM=450 cmd args (export TERM; TERM=450; cmd args) If the -k flag is set, all parameter assignment arguments are placed in the environment, even if they occur after the command name. The command that follows first prints a=b c and then c. echo a=b c set -k echo a=b c Functions The function keyword, described in the ``Commands'' section earlier, is used to define shell functions. Shell functions are read in and stored internally. Alias names are resolved when the function is read. Functions are executed like com- mands with the arguments passed as positional parameters. (See ``Execution'' later in this section.) 14 April, 1990
ksh(1) ksh(1)Functions execute in the same process as the caller and share all files, traps (other than EXIT and ERR), and present working directories with the caller. A trap set on EXIT inside a function is executed after the function com- pletes. Ordinarily, variables are shared between the cal- ling program and the function. However, the typeset special command used within a function defines local variables whose scope includes the current function and all functions it calls. The special command return is used to return from function calls. Errors within functions return control to the call- er. Function identifiers can be listed with the -f option of the typeset special command. The text of functions will also be listed. Function can be undefined with the -f option of the unset special command. Ordinarily, functions are unset when the shell executes a shell script. The -xf option of the typeset command allows a function to be exported to scripts that are executed without a separate invocation of the shell. Functions that need to be defined across separate invocations of the shell should be placed in the ENV file. Jobs If the monitor option of the set command is turned on, an interactive shell associates a job with each pipeline. It keeps a table of current jobs, printed by the jobs command, and assigns them small integer numbers. When a job is started asynchronously with &, the shell prints a line which looks like [1] 1234 indicating that the job which was started asynchronously was job number 1 and had one (top-level) process, whose process ID was 1234. If you are running a job and wish to do something else you may hit CONTROL-Z which sends a STOP signal to the current job. The shell will then normally indicate that the job has been ``Stopped,'' and print another prompt. You can then manipulate the state of this job, putting it in the back- ground with the bg command, or run some other commands and then eventually bring the job back into the foreground with the foreground command fg. A CONTROL-Z takes effect immedi- ately and is similar to an interrupt in that pending output and unread input are discarded when it is typed. April, 1990 15
ksh(1) ksh(1)A job being run in the background will stop if it tries to read from the terminal. Background jobs are normally al- lowed to produce output, but this can be disabled by giving the command stty tostop. If you set this tty option, then background jobs will stop when they try to produce output as they do when they try to read input. There are several ways to refer to jobs in the shell. The character % introduces a job name. If you wish to refer to job number 1, you can give it the name %1. Jobs can also be named with prefixes of the string typed in to start them. Thus, on systems that support job control, fg %ed would nor- mally restart a suspended ed(1) job, provided a suspended job whose name began with the string ed was present. The shell maintains a notion of current and previous jobs. In output pertaining to jobs, the current job is marked with a + and the previous job with a -. The abbreviation %+ refers to the current job and %- refers to the previous job. %% is also a synonym for the current job. This shell knows immediately when the state of a process changes and will generally inform you when a job becomes blocked and no further progress is possible, This informa- tion is offered just before the shell prints a prompt, so as to not be interrupted. When you try to leave the shell while jobs are running or stopped, you will be warned that ``You have stopped (run- ning) jobs''. You may use the jobs command to see what they are. If you use this command or immediately try to exit again, the shell will not warn you a second time, and the stopped jobs will be terminated. Signals The INT and QUIT signals for an invoked command are ignored if the command is followed by an & and the job monitor op- tion is not active. Otherwise, signals have the values in- herited by the shell from its parent (see also the trap com- mand later in this section). Execution Each time a command is executed, the substitutions described are carried out. If the command name matches one of the ``Special Commands'' listed later, it is executed within the current shell process. Next, the command name is checked to see if it matches one of the user defined functions. If it does, the positional parameters are saved and then reset to the arguments of the function call. When the function com- pletes or issues a RETURN, the positional parameter list is restored and any trap set on EXIT within the function is ex- ecuted. The value of a function is the value of the last 16 April, 1990
ksh(1) ksh(1)command executed. A function is also executed in the current shell process. If a command name is not a special command or a user defined function, a process is created and an attempt is made to execute the command via exec(2). The shell parameter PATH defines the search path for the directory containing the command. Alternative directory names are separated by a colon (:). The default path is /bin:/usr/bin: (specifying /bin, /usr/bin, and the current directory in that order). The current directory can be specified by two or more adjacent colons, or by a colon at the beginning or end of the path list. If the command name contains a / then the search path is not used. Otherwise, each directory in the path is searched for an executable file. If the file has execute permission but is not a directory or an a.out file, it is assumed to be a file con- taining shell commands and a subshell is spawned to read it. All nonexported aliases, functions, and named parameters are removed in this case. If the shell command file doesn't have read permission, or if the setuid and/or setgid bits are set on the file, then the shell executes an agent whose job it is to set up the permissions and execute the shell with the shell command file passed down as an open file. A parenthesized command is also executed in a subshell without removing nonexported quantities. Command Re-entry The text of the last HISTSIZE (default 128) commands entered from a terminal device is saved in a history file. The file $HOME/sh_history is used if the HISTFILE variable is not set or is not writable. A shell can access the commands of all interactive shells which use the same named HISTFILE. The special command fc is used to list or edit a portion of this file. The portion of the file to be edited or listed can be selected by number or by typing the first character or char- acters of the command. A single command or range of com- mands can be specified. If you do not specify an editor program as an argument to fc then the value of the parameter FCEDIT is used. If FCEDIT is not defined then /bin/ed is used. The edited command(s) is printed and reexecuted upon leaving the editor. The editor name - is used to skip the editing phase and to re-execute the command. In this case a substitution parameter of the form old=new can be used to modify the command before execution. For example, if r is aliased to 'fc -e -' then typing r bad=good c will reexecute the most recent command which starts with the letter c, re- placing the first occurrence of the string bad with the string good. Inline Editing Options Normally, each command line entered from a terminal device is simply typed and followed by a newline (RETURN or April, 1990 17
ksh(1) ksh(1)LINEFEED). If the vi or emacs option is active, the user can edit the command line. To be in either of these edit modes, set the corresponding option. An editing option is automatically selected each time the VISUAL or EDITOR vari- able is assigned a value ending in either of these option names. The editing features require that the user's terminal accept RETURN as a carriage return without a linefeed and that a space ( ) must overwrite the current character on the screen. Note: ADM terminal users should set the ``space- advance'' switch to ``space''. Hewlett-Packard series 2621 terminal users should set the straps to ``bcGHxZ etX''. The editing modes implement a concept where the user is looking through a window at the current line. The window width is the value of COLUMNS if it is defined, otherwise 80. If the line is longer than the window width minus two, a mark is displayed at the end of the window to notify the user. As the cursor moves and reaches the window boundaries the window will be centered around the cursor. The mark is a > (<, *) if the line extends on the right (left, both) side(s) of the window. The emacs Editing Mode This mode is entered by enabling either the emacs or gmacs option. The only difference between these two modes is the way they handle CONTROL-T. To edit, the user moves the cur- sor to the point needing correction and then inserts or deletes characters or words as needed. All the editing com- mands are control characters or escape sequences. The nota- tion for control characters is caret (^) followed by the character. For example, ^F is the notation for CONTROL-F. The SHIFT key is not depressed. (The notation ^? indicates the DELETE.) The notation for escape sequences is M- followed by a char- acter. For example, M-f (pronounced Meta f) is entered by depressing ESCAPE (ASCII 033) followed by f. (M-F would be the notation for ESCAPE followed by SHIFT (uppercase) F.) All edit commands operate from any place on the line (not just at the beginning). Neither RETURN nor LINEFEED is en- tered after edit commands except when noted. ^F Move cursor forward (right) one character. M-f Move cursor forward one word. (The editor's idea of a word is a string of characters consisting of 18 April, 1990
ksh(1) ksh(1)only letters, digits and underscores.) ^B Move cursor backward (left) one character. M-b Move cursor backward one word. ^A Move cursor to start of line. ^E Move cursor to end of line. ^]char Move cursor to character char on current line. ^X^X Interchange the cursor and mark. erase Delete previous character. (User-defined erase character as defined by the stty command, usually CONTROL-H or #). ^D Delete current character. M-d Delete current word. M-^H Delete previous word. (Meta-backspace) M-h Delete previous word. M-^? Delete previous word (Meta-delete) If your inter- rupt character is ^? (DELETE, the default), then this command will not work. ^T Transpose current character with next character in emacs mode. Transpose two previous characters in gmacs mode. ^C Capitalize current character. M-c Capitalize current word. M-l Change the current word to lowercase. ^K Kill from the cursor to the end of the line. If given a parameter of zero then kill from the start of the line to the cursor. ^W Kill from the cursor to the mark. M-p Push the region from the cursor to the mark on the stack. kill Kill the entire current line. (User-defined kill character as defined by the stty command, usually CONTROL-G or @.) If two kill characters are en- tered in succession, all kill characters following will cause a linefeed (useful when using paper terminals). ^Y Restore last item removed from the line. (Yank item back to the line.) ^L Line feed and print current line. ^@ Set mark. (Null character) M- Set mark. (Meta space) ^J Execute the current line. (Newline) ^M Execute the current line. (RETURN) eof End-of-file character, normally CONTROL-D, will terminate the shell if the current line is null. ^P Fetch previous command. Each time CONTROL-P is entered, the previous command, backward in time, is accessed. M-< Fetch the least recent (oldest) history line. M-> Fetch the most recent (youngest) history line. ^N Fetch next command. Each time CONTROL-n is en- tered, the next command, forward in time, is ac- cessed. April, 1990 19
ksh(1) ksh(1)^Rstring Reverse search history for a previous command line containing string. If a parameter of zero is given, the search is forward. The string is ter- minated by a RETURN or newline character. If string is omitted, then the next command line con- taining the most recent string is accessed. In this case, a parameter of zero reverses the direc- tion of the search. ^O Operate-execute the current line and fetch the next line relative to the current line from the history file. M-digits Define numeric parameter, the digits are taken as a parameter to the next command. (ESCAPE) The commands that accept a parameter are ., CONTROL-F, CONTROL-B, erase, CONTROL-D, CONTROL-K, CONTROL-R, CONTROL-P, CONTROL-n, M-., M-_, M-b, M-c, M-d, M- f, M-h, and M-^H. M-letter Soft-key searches your alias list for an alias by the name _letter and if an alias of this name is defined, its value will be inserted on the input queue. The letter must not be one of the above named meta-functions. M-. The last word of the previous command is inserted on the line. If preceded by a numeric parameter, the value of this parameter determines which word to insert other than the last word. M-_ Same as M-.. M-* Attempts filename generation on the current word. An asterisk is appended if the word doesn't con- tain any special pattern characters. M-ESCAPE Same as M-*. M-= Lists all files matching current word pattern if an asterisk is appended. ^U Multiplies parameter of next command by 4. \ Escape next character. Editing characters, the user's erase, kill, and interrupt (normally ^?) characters, may be entered in a command line or in a search string if preceded by a \. The \ removes the next character's editing features (if any). ^V Display version of the shell. The vi Editing Mode There are two typing modes. Initially, when you enter a command you are in the input mode. To edit, the user enters control mode by typing ESCAPE (033), moves the cursor to the point needing correction, and then inserts or deletes char- acters or words as needed. Most control commands accept an optional repeat count prior to the command. When in vi mode on most systems, canonical processing is in- itially enabled and the command will be echoed again if the speed is 1200 baud or greater, if it contains any control 20 April, 1990
ksh(1) ksh(1)characters, or if less than one second has elapsed since the prompt was printed. The escape character terminates canoni- cal processing for the remainder of the command and the user can then modify the command line. This scheme has the ad- vantages of canonical processing with the type-ahead echoing of raw mode. If the option viraw is also set, the terminal will always have canonical processing disabled. This mode is implicit for systems that do not support two alternate end-of-line delimiters, and may be helpful for certain terminals. Input Edit Commands By default the editor is in input mode. Erase Delete previous character. (User-defined erase character as defined by the stty com- mand, usually CONTROL-H or #.) ^W Delete the previous blank separated word. ^D Terminate the shell. ^V Escape next character. Editing characters, the user's erase or kill characters, may be entered in a command line or in a search string if preceded by a CONTROL-V. The CONTROL-V removes the next character's edit- ing features (if any). \ Escape the next erase or kill character. Motion Edit Commands These commands will move the cursor. [count]l Cursor forward (right) one character. [count]w Cursor forward one alpha-numeric word. [count]W Cursor to the beginning of the next word that follows a blank. [count]e Cursor to the end of the current word. [count]E Cursor to the end of the current blank delim- ited word. [count]h Cursor backward (left) one character. [count]b Cursor backward one word. [count]B Cursor to the preceding blank separated word. [count]fc Find the next character c in the current line. [count]Fc Find the previous character c in the current line. [count]tc Equivalent to f followed by h. [count]Tc Equivalent to F followed by l. ; Repeats the last single character find com- mand, f, F, t, or T. , Reverses the last single character find com- mand. 0 Cursor to the start of the line. April, 1990 21
ksh(1) ksh(1)^ Cursor to the first nonblank character in the line. $ Cursor to the end of the line. Search Edit Commands These commands access your command history. [count]k Fetch previous command. Each time k is en- tered the previous command in time is ac- cessed. [count]- Equivalent to k. [count]j Fetch next command. Each time j is entered the next command in time is accessed. [count]+ Equivalent to j. [count]G The command number count is fetched. The de- fault is the least recent history command. /string Search backward through history for a previ- ous command containing string. The string is terminated by a RETURN or newline. If string is null the previous string will be used. ?string Same as / except that the search will be in the forward direction. n Search for the next match of the last pattern to / or ? commands. N Search for the next match of the last pattern to / or ?, but in reverse direction. Search history for the string insert by the previous / command. Text Modification Edit Commands These commands will modify the line. a Enter input mode and enter text after the current character. A Append text to the end of the line. Equivalent to $a. [count]cmotion c[count]motion Delete from the current character through the character preceding the cursor which was moved by motion. If motion is c, the entire line will be deleted and the input mode en- tered. C Delete from the current character through the end of the line and enter input mode. Equivalent to c$. S Equivalent to cc. D Delete from the current character through the end of the line. Equivalent to d$. [count]dmotion d[count]motion Delete from the current character through the 22 April, 1990
ksh(1) ksh(1)character that motion would move to. If mo- tion is d, the entire line will be deleted. i Enter input mode and insert text before the current character. I Insert text before the beginning of the line. Equivalent to the two character sequence ^i. [count]P Place the previous text modification before the cursor. [count]p Place the previous text modification after the cursor. R Enter input mode and replace the characters on the screen with characters you type in overlay fashion. rc Replace the current character with c. [count]x Delete current character. [count]X Delete preceding character. [count]. Repeat the previous text modification com- mand. ~ Invert the case of the current character and advance the cursor. [count]_ Causes the count word of the previous command to be appended and input mode entered. The last word is used if count is omitted. * Causes an * to be appended to the current word and filename generation is attempted. If no match is found, it rings the bell. Otherwise, the word is replaced by the match- ing pattern and input mode is entered. Other Edit Commands [count]ymotion y[count]motion Yank from the current character through the character that motion would move the cursor to and puts them into the delete buffer. The text and cursor are unchanged. Y Yanks from the current position to the end of the line. Equivalent to y$. u Undo the last text modifying command. U Undo all the text modifying commands per- April, 1990 23
ksh(1) ksh(1)formed on the line. [count]v Returns the command fc -e ${VISUAL:-${EDITOR:-vi}} count in the input buffer. If count is omitted, then the current line is used. ^L Line feed and print current line. Has effect only in the control mode. ^J Execute the current line, regardless of mode. (Newline) ^M Execute the current line, regardless of mode. (RETURN) # Inserts a # before the line and after each newline prior to sending it. Useful for causing the current line to be inserted in the history without being executed. = Lists the filenames that match the current word as if an asterisk were appended to it. @letter Search your alias list for an alias by the name _letter and if an alias of this name is defined, its value will be inserted on the input queue for processing. Special Commands The following simple commands are executed in the shell pro- cess. Input/output redirection is permitted. Unless other- wise indicated, the output is written on file descriptor 1. Commands that are preceded by one or two † are treated spe- cially in the following ways: ⊕ Parameter assignment lists preceding the command remain in effect when the command completes. ⊕ Commands are executed in a separate process when used within command substitution. ⊕ Errors in commands preceded by †† cause the script that contains them to abort. † : [arg ...] The command only expands parameters. A zero exit code is returned. †† . file [arg ...] Read and execute commands from file and return. The commands are executed in the current shell environment. The search path specified by PATH is used to find the directory containing file. If any arguments arg are given, they become the positional parameters. Other- wise the positional parameters are unchanged. alias [-tx] [name [=value] ...] alias with no arguments prints the list of aliases in 24 April, 1990
ksh(1) ksh(1)the form name=value on standard output. An alias is defined for each name whose value is given. A trailing space in value causes the next word to be checked for alias substitution. The -t flag is used to set and list tracked aliases. The value of a tracked alias is the full pathname corresponding to the given name. The value becomes undefined when the value of PATH is reset but the aliases continue to be tracked. Without the -t flag, assigned to each name in the argument list for which no value is given, the name and value of the alias is printed. The -x flag is used to set or print exported aliases. An exported alias is defined across subshell environments. Alias returns true unless a name is given for which no alias has been defined. bg [%job] Puts the specified job into the background. The current job is put in the background if job is not specified. break [n] Exits from the enclosing for, while, until, or select loop, if any. If n is specified, then break n levels. continue [n] Resumes the next iteration of the enclosing for, while, until, or select loop. If n is specified then resume at the nth enclosing loop. † cd [arg] † cd old new This command can be in either of two forms. In the first form it changes the current directory to arg. If arg is - the directory is changed to the previous directory. The shell parameter HOME is the default arg. The parameter PWD is set to the current directo- ry. The shell parameter CDPATH defines the search path for the directory containing arg. Alternative directo- ry names are separated by a colon (:). The default path is <null> (specifying the current directory). Note that the current directory is specified by a null pathname, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If arg begins with a /, then the search path is not used. Otherwise, each directory in the path is searched for arg. The second form of cd substitutes the string new for the string old in PWD, the current directory name, and tries to change to this new directory. echo [-n] [arg...] April, 1990 25
ksh(1) ksh(1)The built-in echo command writes its arguments (separated by blanks and terminated by a RETURN) on the standard output. If the -n flag is used, no newline is added to the output. echo is useful for producing di- agnostics in shell programs and for writing constant data on pipes. To send diagnostics to the standard er- ror file, do echo ... 1>&2 †† eval [arg ... ] The arguments are read as input to the shell and the resulting command(s) are executed. †† exec [arg ... ] If arg is given, the command specified by the arguments is executed in place of this shell without creating a new process. Input/output arguments may appear and af- fect the current process. If no arguments are given, the effect of this command is to modify file descrip- tors as prescribed by the input/output redirection list. In this case, any file descriptor having numbers greater than 2 and are opened with this mechanism, are closed when invoking another program. exit [n] Causes the shell to exit with the exit status specified by n. If n is omitted then the exit status is that of the last command executed. An end-of-file will also cause the shell to exit unless it has the ignoreeof op- tion (see set later in this section) turned on. †† export [name ... ] The given names are marked for automatic export to the environment of subsequently-executed commands. †† fc [-e ename] [-nlr] [first] [last] †† fc -e - [old=new] [command] In the first form, a range of commands from first to last is selected from the last HISTSIZE commands that were typed at the terminal. The arguments first and last may be specified as a number or as a string. A string is used to locate the most recent command that begins with the given string. A negative number is used as an offset to the current command number. If the flag -l, is selected, the commands are listed on standard output. Otherwise, the editor program ename is invoked on a file containing these keyboard com- mands. If ename is not supplied, then the value of the parameter FCEDIT (default /bin/ed) is used as the edi- tor. When editing is complete, the edited command(s) 26 April, 1990
ksh(1) ksh(1)is executed. If last is not specified then it will be set to first. If first is not specified, the default will be the previous command for editing and -16 for listing. The flag -r reverses the order of the com- mands and the flag -n, when listing, suppresses the command numbers. In the second form the command is re-executed after the substitution old=new is per- formed. fg [%job] If job is specified, fg brings it to the foreground. Otherwise, the current job is brought into the fore- ground. jobs [-l] Lists the active jobs; when given the -l option, it lists process IDs in addition to the normal informa- tion. kill [-sig] process ... Sends either the TERM (terminate) signal or the speci- fied signal to the specified jobs or processes. Sig- nals are given either by number or by name (as given in /usr/include/signal.h, stripped of the prefix SIG). The signal numbers and names are listed by kill -l. If the signal being sent is TERM (terminate) or HUP (hang- up), then the job or process will be sent a CONT (con- tinue) signal if it is stopped. The argument process can be either a process ID or a job. let arg ... Each arg is an arithmetic expression to be evaluated. All calculations are executed with long integers and no check for overflow is performed. Expressions consist of constants, named parameters, and operators. The following set of operators, listed in order of decreas- ing precedence, have been implemented: - unary minus ! logical negation * / % multiplication, division, remainder + - addition, subtraction <= >= < > comparison == != equality inequality = arithmetic replacement Subexpressions in parentheses () are evaluated first and can be used to override the precedence rules as listed. The evaluation within a precedence group is from right to left for the = operator and from left to right for the others. April, 1990 27
ksh(1) ksh(1)A parameter name must be a valid identifier. When a parameter is encountered, the value associated with the parameter name is substituted and expression evaluation resumes. Up to 9 levels of recursion are permitted. The return code is 0 if the value of the last expres- sion is nonzero, and 1 if otherwise. †† newgrp [ arg ... ] Equivalent to exec newgrp arg ... print [-Rnprsu[n] ] [arg ...] The shell output mechanism. With no flags or with the flag -, the arguments are printed on standard output as described by echo(1). In raw mode, -R or -r, the es- cape conventions of echo are ignored. The -R option will print all subsequent arguments and options other than -n. The -p option causes the arguments to be written onto the pipe of the process spawned with |& instead of standard output. The -s option causes the arguments to be written onto the history file instead of onto standard output. The -u flag option can be used to specify the one digit file descriptor unit number n on which the output will be placed. The de- fault is 1. If the flag option -n is used, no newline is added to the output. pwd Equivalent to print -r - $PWD read [-prsu [n] ] [name?prompt] [name ...] The shell input mechanism. One line is read and is broken up into words using the characters in IFS as separators. In raw mode, -r, a \ at the end of a line does not signify line continuation. The first word is assigned to the first name, the second word to the second name, and so on, with leftover words assigned to the last name. The -p option causes the input line to be taken from the input pipe of a process spawned by the shell using |&. If the -s flag is present, the in- put will be saved as a command in the history file. The flag -u can be used to specify a one digit file descriptor unit to read from. The file descriptor can be opened with the exec special command. The default value of n is 0. If name is omitted then REPLY is used as the default name. The return code is 0 unless an end-of-file is encountered. An end-of-file with the -p option causes cleanup for this process so another can be spawned. If the first argument contains a ?, the remainder of this word is used as a prompt when the shell is interactive. If the given file descriptor is open for writing and is a terminal device, then the prompt is placed on this unit. Otherwise the prompt is 28 April, 1990
ksh(1) ksh(1)issued on file descriptor 2. The return code is 0 un- less an end-of-file is encountered. †† readonly [name ...] The given names are marked ``read only'' and these names cannot be changed by subsequent assignment. †† return [n] Causes a shell function to return to the invoking script with the return status specified by n. If n is omitted then the return status is that of the last com- mand executed. If return is invoked while not in a function or a . script, then it is the same as an exit. set [-aefhkmnostuvx] [-o option ...] [arg ...] The flags for this command have meaning as follows: -a All subsequent parameters defined are automati- cally exported. -e If the shell is noninteractive and if a command fails, execute the ERR trap, if set, and exit immediately. This mode is disabled while read- ing profiles. -f Disables filename generation. -h Each command whose name is an identifier be- comes a tracked alias when first encountered. -k All parameter assignment arguments are placed in the environment for a command, not just those that precede the command name. -m Background jobs will run in a separate process group and a line will print upon completion. The exit status of background jobs is reported in a completion message. On systems with job control, this flag is turned on automatically for interactive shells. -n Reads commands but does not execute them. Ig- nored for interactive shells. -o The following argument can be one of the fol- lowing names: allexport Same as -a. errexit Same as -e. bgnice All background jobs are run at a April, 1990 29
ksh(1) ksh(1)lower priority. emacs Enters into an emacs style in- line editor for command entry. gmacs Enters into a gmacs style in- line editor for command entry. ignoreeof The shell will not exit on end- of-file. The command exit must be used. keyword Same as -k. markdirs All directory names resulting from filename generation have a trailing / appended. monitor Same as -m. noexec Same as -n. noglob Same as -f. nounset Same as -u. protected Same as -p. verbose Same as -v. trackall Same as -h. vi Enters into insert mode of a vi style inline editor until the escape character 033 is used. This enables the move mode. A RETURN sends the line. viraw Each character is processed as it is typed in vi mode. xtrace Same as -x. If no flag option name is sup- plied, then the current settings are printed. -p Resets the PATH variable to the default value, disables processing of the $HOME/.profile file, and uses the file /etc/suid_profile instead of the ENV file. This mode is automatically en- abled whenever the effective user ID (or group 30 April, 1990
ksh(1) ksh(1)ID) is not equal to the real user ID (or group ID). -s Sorts the positional parameters. -t Exits after reading and executing one command. -u Treats unset parameters as an error when sub- stitution is necessary. -v Prints shell input lines as they are read. -x Prints commands and their arguments as they are executed. - Turns off -x and -v flags and stops examining arguments for flags. -- Does not change any of the flags; useful in setting $1 to a value beginning with -. If no arguments follow this flag, then the positional parameters are unset. Using + rather than - causes these flags to be turned off. These flags can also be used upon invocation of the shell. The current set of flags may be found in $-. The remaining arguments are positional parameters and are assigned, in order, to $1 $2 .... If no argu- ments are given then the values of all names are print- ed on the standard output. † shift [n] The positional parameters from $n+1 ... are renamed $1 ...; default n is 1. The parameter n can be any arith- metic expression that evaluates to a non-negative number less than or equal to $#. test [expr] Evaluate conditional expression, expr. test evaluates the expression expr and, if its value is true, returns a zero (true) exit status; otherwise, a nonzero (false) exit status is returned; test also returns a nonzero exit status if there are no arguments. The superuser is always granted execute permission even though (1) execute permission is meaningful only for directories and regular files, and (2) exec requires that at least one execute mode bit be set for a regular file to be executable. The following primitives are used to con- struct expr. -r file True if file exists and is readable. April, 1990 31
ksh(1) ksh(1)-w file True if file exists and is writable. -x file True if file exists and is executable. -f file True if file exists and is a regular file. -d file True if file exists and is a directory. -c file True if file exists and is a character special file. -b file True if file exists and is a block special file. -p file True if file exists and is a named pipe (FIFO). -u file True if file exists and its set-user-ID bit is set. -g file True if file exists and its set-group-ID bit is set. -k file True if file exists and its sticky bit is set. -s file True if file exists and has a size greater than zero. -t [fildes] True if the open file whose file descrip- tor number is fildes (1 by default) is as- sociated with a terminal device. -z s1 True if the length of string s1 is zero. -n s1 True if the length of the string s1 is nonzero. s1 = s2 True if strings s1 and s2 are identical. s1 != s2 True if strings s1 and s2 are not identi- cal. s1 True if s1 is not the null string. n1 -eq n2 True if the integers n1 and n2 are alge- braically equal. Any of the comparisons: -ne, -gt, -ge, -lt, and -le may be used in place of -eq. These primaries may be combined with the following operators: 32 April, 1990
ksh(1) ksh(1)! Unary negation operator. -a Binary AND operator. -o Binary OR operator (-a has higher pre- cedence than -o). (expr) Parentheses for grouping. Notice that all the operators and flags are separate arguments to test. Notice also that parentheses are meaningful to the shell and therefore, must be escaped. test is typically used in shell scripts as in the following example, which prints the message ``foo is a directory'' if it is found to be one when test is run. if test -d foo then echo "foo is a dir" fi the arithmetic comparison operators are not restricted to integers. They allow any arithmetic expression. Four addi- tional primitive expressions are allowed: -L file True, if file is a symbolic link. file1 -nt file2 True, if file1 is newer than file2. file1 -ot file2 True, if file1 is older than file2. file1 -ef file2 True, if file1 has the same device and inode number as file2. times Prints the accumulated user and sys- tem times for the shell and for processes run from the shell. trap [ arg ] [ sig ] ... The command arg is to be read and ex- ecuted when the shell receives signal(s) sig. (Note that arg is scanned once when the trap is set and once when the trap is taken.) Each sig can be given as a number or as the name of the signal. Trap com- mands are executed in order of signal April, 1990 33
ksh(1) ksh(1)number. Any attempt to set a trap on a signal that was ignored on entry to the current shell is ineffective. If arg is omitted or is -, then all trap(s) sig are reset to their origi- nal values. If arg is the null string then this signal is ignored by the shell and by the commands it in- vokes. If sig is ERR then arg will be executed whenever a command has a nonzero exit code. This trap is not inherited by functions. If sig is 0 or EXIT and the trap statement is ex- ecuted inside the body of a function, then the command arg is executed after the function completes. If sig is 0 or EXIT for a trap set outside any function, then the command arg is executed on exit from the shell. The trap command with no arguments prints a list of commands associated with each signal number. †† typeset [-HLRZfilprtux [n] [name [=value] ] ... ] When invoked inside a function, a new instance of the parameter name is created. The parameter value and type are restored when the function completes. The following list of at- tributes may be specified: -H This flag provides A/UX to host namefile mapping on non- UNIX(Reg.) machines. -L Justifies left and removes lead- ing blanks from value. If n is nonzero, it defines the width of the field, otherwise the width is determined by the width of the value of first assignment. When the parameter is assigned to, it is filled on the right with blanks or truncated, if necessary, to fit into the field. Leading zeros are re- moved if the -Z flag is also set. The -R flag is turned off. -R Justifies right and fills with leading blanks. If n is nonzero, it defines the width of 34 April, 1990
ksh(1) ksh(1)the field, otherwise the width is determined by the width of the value of first assignment. The field is filled with blanks or truncated from the end if the parameter is reassigned. The L flag is turned off. -Z justifies right and fills with leading zeros if the first non- blank character is a digit and the -L flag has not been set. If the -L flag has been set, the field is left adjusted and any leading zeros are removed. If n is nonzero, it defines the width of the field; otherwise the width is determined by the width of the value of first assign- ment. -f The names refer to function names rather than parameter names. No assignments can be made and the only other valid flags are -t, which turns on execution-tracing for this func- tion and -x, to allow the func- tion to remain in effect across shell procedures executed in the same process environment. -i Parameter is an integer. This makes arithmetic faster. If n is nonzero it defines the output arithmetic base, otherwise the first assignment determines the output base. -l All uppercase characters con- verted to lowercase. The upper- case flag, -u is turned off. -p The output of this command, if any, is written onto the two-way pipe. -r The given names are marked read only and these names cannot be changed by subsequent assign- ment. April, 1990 35
ksh(1) ksh(1)-t Tags the named parameters. Tags are user-definable and have no special meaning to the shell. -u All lowercase characters are converted to uppercase charac- ters. The lowercase flag, -l is turned off. -x The given names are marked for automatic export to the environ- ment of subsequently-executed commands. Using + rather than - causes these flags to be turned off. If no name arguments are given but flags are specified, a list of names (and op- tionally the values) of the parame- ters which have these flags set is printed. (Using + rather than - keeps the values to be printed.) If no names and flags are given, the names and attributes of all parame- ters are printed. ulimit [-f] [n] -f Imposes a size limit of n 512- byte blocks on files written by child processes (files of any size may be read). This is the default. If n is not given, the current limit is printed. When using the ulimit feature, a regular user is only allowed to bring resource limits down. However, only the superuser can return the limit to a higher status. umask [nnn] The user file-creation mask is set to nnn (see umask(2)). If nnn is omit- ted, the current value of the mask is printed. unalias name ... The parameters given by the list of names are removed from the alias list. unset [-f] name ... 36 April, 1990
ksh(1) ksh(1)The parameters given by the list of names are unassigned. That is, their values and attributes are erased. Read only variables cannot be unset. If the flag, -f, is set, then the names refer to function names. wait [n ] Waits for the specified child process and reports its termination status. If n is not given then all currently active child processes are waited for. The return code from this com- mand is that of the process waited for. whence [-v] name ... For each name, indicate how it would be interpreted if used as a command name. The flag, -v, produces a more verbose report. Invocation If the shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is assumed to be a login shell and commands are read from /etc/profile and then from either .profile in the current directory or $HOME/.profile, if either file exists. Next, commands are read from the file named by performing parameter substitu- tion on the value of the environment parameter ENV if the file exists. If the -s flag is not present and arg is, then a path search is performed on the first arg to determine the name of the script to execute. The script arg must have read permission and any setuid and setgid settings will be ignored. Commands are then read as described later; the following flags are interpreted by the shell when it is in- voked. -c string If the -c flag is present then commands are read from string. -s If the -s flag is present or if no arguments remain, then commands are read from the standard input. Shell output, except for the output of the ``Special Commands'' listed earlier, is written to file descriptor 2. -i If the -i flag is present or if the shell input and output are attached to a terminal (as told by ioctl(2)) then this shell is interactive. In this case TERM is ignored (so that kill 0 does not kill April, 1990 37
ksh(1) ksh(1)an interactive shell) and INTR is caught and ig- nored (so that wait is interruptible). In all cases, QUIT is ignored by the shell. -r If the -r flag is present, the shell is a res- tricted shell and is used to set up login names and execution environments whose capabilities are more controlled than those of the standard shell. The actions of the restricted shell are identical to those of ksh, except that changing the directo- ry, setting the value of SHELL, ENV, or PATH, specifying path or command names containing /, and redirecting output (> and >>) are disallowed. The restrictions above are enforced after .profile and the ENV files are interpreted. When a command to be executed is found to be a shell pro- cedure, the restricted shell invokes ksh to execute it. Thus, it is possible to provide to the end-user shell pro- cedures that have access to the full power of the standard shell, while imposing a limited menu of commands; this scheme assumes that the end-user does not have write and ex- ecute permissions in the same directory. The net effect of these rules is that the writer of the .profile, by performing guaranteed setup actions and leaving the user in an appropriate directory (probably not the login directory), has complete control over user actions. The system administrator often sets up a directory of com- mands (for example, /usr/rbin) that can be safely invoked by the restricted shell. Some systems also provide a restrict- ed editor red. The remaining flags and arguments are described under the set command earlier. EXIT STATUS Errors detected by the shell, such as syntax errors, cause the shell to return a nonzero exit status. Otherwise, the shell returns the exit status of the last command executed (see also the exit command earlier). If the shell is being used noninteractively, then execution of the shell file is abandoned. Runtime errors detected by the shell are report- ed by printing the command or function name and the error condition. If the line number that the error occurred on is greater than one, then the line number is also printed in square brackets ([]) after the command or function name. 38 April, 1990
ksh(1) ksh(1)FILES /bin/ksh /etc/passwd /etc/profile /etc/suid_profile $HOME/.profile /tmp/ksh* /dev/null SEE ALSO cat(1), csh(1), echo(1), ed(1), env(1), newgrp(1), sh(1), vi(1), dup(2), exec(2), fork(2), ioctl(2), lseek(2), pipe(2), umask(2), ulimit(2), wait(2), rand(3), signal(3), a.out(4), profile(4), environ(5). ``Korn Shell Reference'' in A/UX User Interface. CAVEATS If a command which is a tracked alias is executed, and then a command with the same name is installed in a directory in the search path prior to the directory where the original command was found, the shell will continue to exec the ori- ginal command. Use the -t option of the alias command to correct this situation. Some very old shell scripts contain a ^ as a synonym for the pipe character |. If a command is piped into a shell command, then all vari- ables set in the shell command are lost when the command completes. Using the fc built-in command within a compound command will cause the whole command to disappear from the history file. The built-in command .file reads the whole file before any commands are executed. Therefore, alias and unalias com- mands in the file will not apply to any functions defined in the file. April, 1990 39