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GETUSERSHELL(3)            Linux Programmer's Manual           GETUSERSHELL(3)
NAME
       getusershell, setusershell, endusershell - get permitted user shells
SYNOPSIS
       #include <unistd.h>
       char *getusershell(void);
       void setusershell(void);
       void endusershell(void);
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
       getusershell(), setusershell(), endusershell():
           Since glibc 2.21:
               _DEFAULT_SOURCE
           In glibc 2.19 and 2.20:
               _DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
           Up to and including glibc 2.19:
               _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
DESCRIPTION
       The  getusershell()  function  returns  the  next  line  from  the file
       /etc/shells, opening the file if necessary.  The  line  should  contain
       the  pathname  of a valid user shell.  If /etc/shells does not exist or
       is unreadable, getusershell() behaves as if /bin/sh and  /bin/csh  were
       listed in the file.
       The setusershell() function rewinds /etc/shells.
       The endusershell() function closes /etc/shells.
RETURN VALUE
       The getusershell() function returns NULL on end-of-file.
FILES
       /etc/shells
ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).
       +--------------------------------+---------------+-----------+
       |Interface                       | Attribute     | Value     |
       +--------------------------------+---------------+-----------+
       |getusershell(), setusershell(), | Thread safety | MT-Unsafe |
       |endusershell()                  |               |           |
       +--------------------------------+---------------+-----------+
CONFORMING TO
       4.3BSD.
SEE ALSO
       shells(5)
COLOPHON
       This page is part of release 4.15 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.
GNU                               2016-03-15                   GETUSERSHELL(3)