unistd(4)                        UNIX System V                        unistd(4)


NAME
      unistd - header file for symbolic constants

SYNOPSIS
      #include <unistd.h>

DESCRIPTION
      The unistd.h header file defines the symbolic constants and structures
      not already defined or declared in some other header file.  The contents
      of this file are shown below.

      The following symbolic constants are defined for the access function [see
      access(2)]:

            ROK        Test for read permission.
            WOK        Test for write permission.
            XOK        Test for execute (search) permission.
            FOK        Test for existence of file.

      The constants FOK, ROK, WOK and XOK and the expressions ROK|WOK,
      ROK|XOK and ROK|WOK|XOK all have distinct values.

      Declares the constant

            NULL        null pointer

      The following symbolic constants are defined for the lockf function [see
      lockf(3C)]:

            FULOCK     Unlock a previously locked region.
            FLOCK      Lock a region for exclusive use.
            FTLOCK     Test and lock a region for exclusive use.
            FTEST      Test a region for other processes locks.

      The following symbolic constants are defined for the lseek [see lseek(2)]
      and fcntl [see fcntl(2)] functions (they have distinct values):

            SEEKSET    Set file offset to offset.
            SEEKCUR    Set file offset to current plus offset.
            SEEKEND    Set file offset to EOF plus offset.

      The following symbolic constants are defined (with fixed values):

            POSIXVERSION          Integer value indicating version of the
                                    POSIX standard.
            XOPENVERSION          Integer value indicating version of the XPG
                                    to which system is compliant.

      The following symbolic constants are defined to indicate that the option
      is present:




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unistd(4)                        UNIX System V                        unistd(4)


            POSIXJOBCONTROL      Implementation supports job control.
            POSIXSAVEDIDS        The exec functions [see exec(2)] save the
                                    effective user and group.
            POSIXVDISABLE         Terminal special characters defined in
                                    termios.h [see termio(7)] can be disabled
                                    using this character.

      The following symbolic constants are defined for sysconf [see
      sysconf(3C)]:
            SCARGMAX
            SCCHILDMAX
            SCCLKTCK
            SCJOBCONTROL
            SCNGROUPSMAX
            SCOPENMAX
            SCPAGESIZE
            SCPASSMAX
            SCSAVEDIDS
            SCVERSION
            SCXOPENVERSION

      The following symbolic constants are defined for pathconf [see
      fpathconf(2)]:
            PCCHOWNRESTRICTED
            PCLINKMAX
            PCMAXCANON
            PCMAXINPUT
            PCNAMEMAX
            PCNOTRUNC
            PCPATHMAX
            PCPIPEBUF
            PCVDISABLE

      The following symbolic constants are defined for file streams:

            STDINFILENO            File number of stdin.  It is 0.
            STDOUTFILENO           File number of stout.  It is 1.
            STDERRFILENO           File number of stderr.  It is 2.

      The following pathnames are defined:

            GFPATH                 Pathname of the group file.
            PFPATH                 Pathname of the passwd file.

NOTES
      The following values for constants are defined for this release of System
      V:

            POSIXVERSION          198808L
            XOPENVERSION          3




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unistd(4)                        UNIX System V                        unistd(4)


SEE ALSO
      access(2), exec(2), fcntl(2), fpathconf(2), lseek(2), termios(2),
      sysconf(3C), group(4), passwd(4), termio(7)



















































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