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Top Forums Programming Is the cd cmd part of the kernel? Post 302519870 by steadyonabix on Thursday 5th of May 2011 09:12:55 AM
Old 05-05-2011
Is the cd cmd part of the kernel?

Hi All

I'm looking at writing something that handles changing directory in the calling shell and wanted to take a look at the cd command.
Code:
which cd

comes back with nothing and
Code:
man cd

does nothing either.

Where is the cd command?

I can see why it wouldn't be with the rest of the commands in /bin as it wouldn't change the directory in the calling shell if it was run in a sub-shell like the other commands are.

Is it part of the kernel?

If so would it be possible to write a kernel module to do what I want? I've been looking at tutorials on kernel programming but haven't found anything that tells me if I can extend the basic Unix command set this way. Most of the examples seem to be driver oriented or basic hello world examples writing to the logs.

Any help appreciated

Cheers
 

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CHSH(1)                                                            User Commands                                                           CHSH(1)

NAME
chsh - change login shell SYNOPSIS
chsh [options] [LOGIN] DESCRIPTION
The chsh command changes the user login shell. This determines the name of the user's initial login command. A normal user may only change the login shell for her own account; the superuser may change the login shell for any account. OPTIONS
The options which apply to the chsh command are: -h, --help Display help message and exit. -R, --root CHROOT_DIR Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory. -s, --shell SHELL The name of the user's new login shell. Setting this field to blank causes the system to select the default login shell. If the -s option is not selected, chsh operates in an interactive fashion, prompting the user with the current login shell. Enter the new value to change the shell, or leave the line blank to use the current one. The current shell is displayed between a pair of [ ] marks. NOTE
The only restriction placed on the login shell is that the command name must be listed in /etc/shells, unless the invoker is the superuser, and then any value may be added. An account with a restricted login shell may not change her login shell. For this reason, placing /bin/rsh in /etc/shells is discouraged since accidentally changing to a restricted shell would prevent the user from ever changing her login shell back to its original value. FILES
/etc/passwd User account information. /etc/shells List of valid login shells. /etc/login.defs Shadow password suite configuration. SEE ALSO
chfn(1), login.defs(5), passwd(5). shadow-utils 4.5 01/25/2018 CHSH(1)
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