unistd(4)                                                         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 which are not already defined or declared in some other
         header. The contents of this header 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










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   unistd(4)                                                         unistd(4)


         The following symbolic constants are defined to indicate that the
         option is present:
            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(3C)]:
            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:







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   unistd(4)                                                         unistd(4)


            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

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









































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