thkukuk / libusershell_econf

Implementation of getusershell() and releated functions using libeconf to read /etc/shells

usershell_econf

This is a small library replacing the setusershell(), getusershell() and endusershell() functions of glibc with a variant, which uses libeconf to read the valid shells following the Configuration Files Specification of the Linux Userspace API Group.

Building and installing usershell_econf

Building

usershell_econf requires libeconf in version 0.4.9 or newer and meson version 0.58 or newer.

Building with meson is quite simple:

$ meson setup build
$ meson compile -C build
$ meson test -C build

If you want to build with the address sanitizer enabled, add -Db_sanitize=address as an argument to meson setup build.

Installing

$ sudo meson install -C build

Usage

There are two ways to use the new functions:

Override glibc functions

The glibc functions can be replaced without further code changes by additionally linking the application against libusershell_econf. It is important that the linker does not optimize away the library, this can happen if e.g. as-needed is used for linking.

Use new function names

To avoid problems, it's recommended to modify the applications source code and exchange all function calls by appending _econf to them:

• setusershell() -> setusershell_econf()
• getusershell() -> getusershell_econf()
• endusershell() -> endusershell_econf()

Additional you need to include an additional header file: #include <usershell_econf.h>

and link against libusershell_econf.

Example code:

...
#include <usershell_econf.h>
...
int
main (void)
{
  char *shell;

...

  setusershell_econf ();
  while ((shell = getusershell_econf ()) != NULL)
    printf ("[%s]\n", shell);
  endusershell_econf ();
...
}

Licensing

See the file COPYING for full text and copying restrictions.