FreeBSD/Linux Kernel Cross Reference
sys/include/limits.h

     /* The <limits.h> header defines some basic sizes, both of the language types 
      * (e.g., the number of bits in an integer), and of the operating system (e.g.
      * the number of characters in a file name.
      */
     
     #ifndef _LIMITS_H
     #define _LIMITS_H
     
     /* Definitions about chars (8 bits in MINIX, and signed). */
    #define CHAR_BIT           8    /* # bits in a char */
    #define CHAR_MIN        -128    /* minimum value of a char */
    #define CHAR_MAX         127    /* maximum value of a char */
    #define SCHAR_MIN       -128    /* minimum value of a signed char */
    #define SCHAR_MAX        127    /* maximum value of a signed char */
    #define UCHAR_MAX        255    /* maximum value of an unsigned char */
    #define MB_LEN_MAX         1    /* maximum length of a multibyte char */
    
    /* Definitions about shorts (16 bits in MINIX). */
    #define SHRT_MIN  (-32767-1)    /* minimum value of a short */
    #define SHRT_MAX       32767    /* maximum value of a short */
    #define USHRT_MAX     0xFFFF    /* maximum value of unsigned short */
    
    /* _EM_WSIZE is a compiler-generated symbol giving the word size in bytes. */
    #if _EM_WSIZE == 2
    #define INT_MIN   (-32767-1)    /* minimum value of a 16-bit int */
    #define INT_MAX        32767    /* maximum value of a 16-bit int */
    #define UINT_MAX      0xFFFF    /* maximum value of an unsigned 16-bit int */
    #endif
    
    #if _EM_WSIZE == 4
    #define INT_MIN (-2147483647-1) /* minimum value of a 32-bit int */
    #define INT_MAX   2147483647    /* maximum value of a 32-bit int */
    #define UINT_MAX  0xFFFFFFFF    /* maximum value of an unsigned 32-bit int */
    #endif
    
    /*Definitions about longs (32 bits in MINIX). */
    #define LONG_MIN (-2147483647L-1)/* minimum value of a long */
    #define LONG_MAX  2147483647L   /* maximum value of a long */
    #define ULONG_MAX 0xFFFFFFFFL   /* maximum value of an unsigned long */
    
    #include <sys/dir.h>
    
    /* Minimum sizes required by the POSIX P1003.1 standard (Table 2-3). */
    #ifdef _POSIX_SOURCE            /* these are only visible for POSIX */
    #define _POSIX_ARG_MAX    4096  /* exec() may have 4K worth of args */
    #define _POSIX_CHILD_MAX     6  /* a process may have 6 children */
    #define _POSIX_LINK_MAX      8  /* a file may have 8 links */
    #define _POSIX_MAX_CANON   255  /* size of the canonical input queue */
    #define _POSIX_MAX_INPUT   255  /* you can type 255 chars ahead */
    #define _POSIX_NAME_MAX DIRSIZ  /* a file name may have 14 chars */
    #define _POSIX_NGROUPS_MAX   0  /* supplementary group IDs are optional */
    #define _POSIX_OPEN_MAX     16  /* a process may have 16 files open */
    #define _POSIX_PATH_MAX    255  /* a pathname may contain 255 chars */
    #define _POSIX_PIPE_BUF    512  /* pipes writes of 512 bytes must be atomic */
    #define _POSIX_STREAM_MAX    8  /* at least 8 FILEs can be open at once */
    #define _POSIX_TZNAME_MAX    3  /* time zone names can be at least 3 chars */
    #define _POSIX_SSIZE_MAX 32767  /* read() must support 32767 byte reads */
    
    /* Values actually implemented by MINIX (Tables 2-4, 2-5, 2-6, and 2-7). */
    /* Some of these old names had better be defined when not POSIX. */
    #define _NO_LIMIT          100  /* arbitrary number; limit not enforced */
    
    #define NGROUPS_MAX          0  /* supplemental group IDs not available */
    #if _EM_WSIZE > 2
    #define ARG_MAX          16384  /* # bytes of args + environ for exec() */
    #else
    #define ARG_MAX           4096  /* args + environ on small machines */
    #endif
    #define CHILD_MAX    _NO_LIMIT  /* MINIX does not limit children */
    #define OPEN_MAX            20  /* # open files a process may have */
    #if 0                   /* V1 file system */
    #define LINK_MAX      CHAR_MAX  /* # links a file may have */
    #else                   /* V2 or better file system */
    #define LINK_MAX      SHRT_MAX  /* # links a file may have */
    #endif
    #define MAX_CANON          255  /* size of the canonical input queue */
    #define MAX_INPUT          255  /* size of the type-ahead buffer */
    #define NAME_MAX        DIRSIZ  /* # chars in a file name */
    #define PATH_MAX           255  /* # chars in a path name */
    #define PIPE_BUF          7168  /* # bytes in atomic write to a pipe */
    #define STREAM_MAX          20  /* must be the same as FOPEN_MAX in stdio.h */
    #define TZNAME_MAX           3  /* maximum bytes in a time zone name is 3 */
    #define SSIZE_MAX        32767  /* max defined byte count for read() */
    
    #endif /* _POSIX_SOURCE */
    
    #endif /* _LIMITS_H */

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