Chsh

Template:Lowercase Template:Infobox Software chsh (an abbreviation of "change shell") is a command on Unix-like operating systems that is used to change a login shell. Users can either supply the pathname of the shell that they wish to change to on the command line, or supply no arguments, in which case Template:Mono allows the user to change the shell interactively.

Usage

Template:Mono is a setuid program that modifies the Template:Mono file, and only allows ordinary users to modify their own login shells. The superuser can modify the shells of other users, by supplying the name of the user whose shell is to be modified as a command-line argument. For security reasons, the shells that both ordinary users and the superuser can specify are limited by the contents of the Template:Mono file, with the pathname of the shell being required to be exactly as it appears in that file. (This security feature is alterable by re-compiling the source code for the command with a different configuration option, and thus is not necessarily enabled on all systems.) The superuser can, however, also modify the password file directly, setting any user's shell to any executable file on the system without reference to Template:Mono and without using Template:Mono.

On most systems, when Template:Mono is invoked without the Template:Mono command-line option (to specify the name of the shell), it prompts the user to select one. On Mac OS X, if invoked without the Template:Mono option, Template:Mono displays a text file in the default editor (initially set to vim) allowing the user to change all of the features of their user account that they are permitted to change, the pathname of the shell being the name next to "Shell:". When the user quits vim, the changes made there are transferred to the /etc/passwd file which only root can change directly.

Using the Template:Mono option (for example: % chsh -s /usr/local/bin/bash) greatly simplifies the task of changing shells.

Depending on the system, Template:Mono may or may not prompt the user for a password before changing the shell, or entering interactive mode. On some systems, use of Template:Mono by non-root users is disabled entirely by the sysadmin.

On many Linux distributions, the Template:Mono command is a PAM-aware application. As such, its behaviour can be tailored, using PAM configuration options, for individual users. For example, an Template:Mono directive that specifies the Template:Mono module can be used to deny Template:Mono access to individual users, by specifying a file of the usernames to deny access to with the Template:Mono option to that module (along with the Template:Mono option).

Portability

POSIX does not describe utilities such as Template:Mono, which are used for modifying the user's entry in Template:Mono. Most Unix-like systems provide Template:Mono. SVr4-based systems provided a similar capability with passwd. Two of the three remaining systems (IBM AIX and HP-UX) provide Template:Mono in addition to Template:Mono. The exception is Solaris, where non-administrators are unable to change their shell unless a network name server such as NIS or NIS+ is installed. The obsolete SGI SVr4 system IRIX64 also lacked Template:Mono.

See also

• Comparison of command shells

Further reading

• — some examples of invoking Template:Mono with the Template:Mono and Template:Mono options

External links

• [[[:Template:Man/4.2BSD]] chsh(Template:Man/4.2BSD)] – Template:Man/4.2BSD
• chsh(1): change your login shell – Linux User Commands Manual
• Template:Apple man page
• passwd(1) – Solaris 11.4 User Commands Reference Manual