getusershell, setusershell, endusershell - get permitted user shells

       For an explanation of the terms used in this section, see attributes(7).
       ┌───────────────────────────────────────────────────────────────────────────┬───────────────┬───────────┐
       │ Interface                                                                 │ Attribute     │ Value     │
       ├───────────────────────────────────────────────────────────────────────────┼───────────────┼───────────┤
       │ getusershell(), setusershell(), endusershell()                            │ Thread safety │ MT-Unsafe │
       └───────────────────────────────────────────────────────────────────────────┴───────────────┴───────────┘

       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.

/etc/shells

       4.3BSD.

       Standard C library (libc, -lc)

       getusershell, setusershell, endusershell - get permitted user shells

       The getusershell() function returns NULL on end-of-file.

shells(5)

Linux man-pages 6.9.1                              2024-05-02                                    getusershell(3)

       None.

#include<unistd.h>char*getusershell(void);voidsetusershell(void);voidendusershell(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)