limits(4) — FILE FORMATS
NAME
limits − header file for implementation-specific constants
SYNOPSIS
#include <limits.h>
DESCRIPTION
The header file limits.h is a list of minimal magnitude limitations imposed by a specific implementation of the operating system.
| CHAR_BIT | 8 | /∗ max # of bits in a "char" ∗/ |
| CHAR_MAX | 127 | /∗ max value of a "char" ∗/ |
| CHAR_MIN | 128 | /∗ min value of a "char" ∗/ |
| CHILD_MAX | 25 | /∗ max # of processes per user id ∗/ |
| CLK_TCK | 100 | /∗ clock ticks per second ∗/ |
| DBL_DIG | 15 | /∗ digits of precision of a "double" ∗/ |
| DBL_MAX | 1.7976931348623157E+308 | /∗ max decimal value of a "double"∗/ |
| DBL_MIN | 2.2250738585072014E-308 | /∗ min decimal value of a "double"∗/ |
| FCHR_MAX | 1048576 | /∗ max size of a file in bytes ∗/ |
| FLT_DIG | 6 | /∗ digits of precision of a "float" ∗/ |
| FLT_MAX | 3.40282347e+38F | /∗ max decimal value of a "float" ∗/ |
| FLT_MIN | 1.17549435E-38F | /∗ min decimal value of a "float" ∗/ |
| INT_MAX | 2147483647 | /∗ max value of an "int" ∗/ |
| INT_MIN | (-2147483647-1) | /∗ min value of an "int" ∗/ |
| LINK_MAX | 1024 | /∗ max # of links to a single file ∗/ |
| LOGNAME_MAX | 8 | /∗ max # of characters in a login name ∗/ |
| LONG_BIT | 32 | /∗ # of bits in a "long" ∗/ |
| LONG_MAX | 2147483647 | /∗ max value of a "long int" ∗/ |
| LONG_MIN | (-2147483647-1) | /∗ min value of a "long int" ∗/ |
| MAX_CANON | 255 | /∗ max bytes in a line for canonical |
| processing ∗/ | ||
| MAX_INPUT | 512 | ∗ max size of a char input buffer ∗/ |
| MB_LEN_MAX | 5 | /∗ max # of bytes in a multibyte |
| character ∗/ | ||
| NAME_MAX | 14 | /∗ max # of characters in a file name ∗/ |
| NGROUPS_MAX | 16 | /∗ max # of groups for a user ∗/ |
| NL_ARGMAX | 9 | /∗ max value of "digit" in calls to the |
| NLS printf() and scanf() ∗/ | ||
| NL_LANGMAX | 14 | /∗ max # of bytes in a LANG name ∗/ |
| NL_MSGMAX | 32767 | /∗ max message number ∗/ |
| NL_NMAX | 1 | /∗ max # of bytes in N-to-1 mapping |
| characters ∗/ | ||
| NL_SETMAX | 255 | /∗ max set number ∗/ |
| NL_TEXTMAX | 255 | /∗ max # of bytes in a message string ∗/ |
| NZERO | 20 | /∗ default process priority ∗/ |
| OPEN_MAX | 25 | /∗ max # of files a process can have |
| open ∗/ | ||
| PASS_MAX | 8 | /∗ max # of characters in a password ∗/ |
| PATH_MAX | 1024 | /∗ max # of characters in a path name ∗/ |
| PID_MAX | 30000 | /∗ max value for a process ID ∗/ |
| PIPE_BUF | 5120 | /∗ max # bytes atomic in write to a pipe ∗/ |
| PIPE_MAX | 5120 | /∗ max # bytes written to a pipe |
| in a write ∗/ | ||
| SCHAR_MAX | 127 | /∗ max value of a "signed char" ∗/ |
| SCHAR_MIN | (-128) | /∗ min value of a "signed char" ∗/ |
| SHRT_MAX | 32767 | /∗ max value of a "short int" ∗/ |
| SHRT_MIN | (-32768) | /∗ min value of a "short int" ∗/ |
| STD_BLK | 1024 | /∗ # bytes in a physical I/O block ∗/ |
| SYS_NMLN | 256 | /∗ 4.0 size of utsname elements ∗/ |
| /∗ also defined in sys/utsname.h ∗/ | ||
| SYSPID_MAX | 1 | /∗ max pid of system processes ∗/ |
| UCHAR_MAX | 255 | /∗ max value of an "unsigned char" ∗/ |
| UID_MAX | 60002 | /∗ max value for a user or group ID ∗/ |
| UINT_MAX | 4294967295 | /∗ max value of an "unsigned int" ∗/ |
| ULONG_MAX | 4294967295 | /∗ max value of an "unsigned long int" ∗/ |
| USHRT_MAX | 65535 | /∗ max value of an "unsigned short int" ∗/ |
| USI_MAX | 4294967295 | /∗ max decimal value of an "unsigned" ∗/ |
| WORD_BIT | 32 | /∗ # of bits in a "word" or "int" ∗/ |
The following POSIX definitions are the most restrictive values to be used by a POSIX conformant application. Conforming implementations shall provide values at least this large.
| _POSIX_ARG_MAX | 4096 | /∗ max length of arguments to exec ∗/ |
| _POSIX_CHILD_MAX | 6 | /∗ max # of processes per user ID ∗/ |
| _POSIX_LINK_MAX | 8 | /∗ max # of links to a single file ∗/ |
| _POSIX_MAX_CANON | 255 | /∗ max # of bytes in a line of input ∗/ |
| _POSIX_MAX_INPUT | 255 | /∗ max # of bytes in terminal |
| input queue ∗/ | ||
| _POSIX_NAME_MAX | 14 | /∗ # of bytes in a filename ∗/ |
| _POSIX_NGROUPS_MAX | 0 | /∗ max # of groups in a process ∗/ |
| _POSIX_OPEN_MAX | 16 | /∗ max # of files a process can have open ∗/ |
| _POSIX_PATH_MAX | 255 | /∗ max # of characters in a pathname ∗/ |
| _POSIX_PIPE_BUF | 512 | /∗ max # of bytes atomic in write |
| to a pipe ∗/ |