Why doesn't "cd" work in a bash shell script?

Question

I'm trying to write a small script to change the current directory to my project directory:

#!/bin/bash
cd /home/askgelal/projects/java

I saved this file as proj, changed the chmod, copied it to /usr/bin. When I call it by: proj, it does nothing. What am I doing wrong?

Answer 1

Shell scripts are run inside a subshell, and each subshell has its own concept of what the current directory is. The cd succeeds, but as soon as the subshell exits, the previous current directory is restored.

One way to get around this is to use an alias instead:

alias proj="cd /home/askgelal/projects/java"

Answer 2

Nothing. You've changed the directory, but only within the subshell that runs the script.

You can run the script in your current process with the "dot" command:

. proj

But I'd prefer Greg's suggestion to use an alias in this simple case.

Answer 3

When you fire a shell script, it runs a new instance of that shell (/bin/bash). Thus, your script just fires up a shell, changes the directory and exits. Put another way, cd (and other such commands) within a shell script do not affect nor have access to the shell from which they were launched.

Answer 4

It only changes the directory for the script itself, while your current directory stays the same.

You might want to use a symbolic link instead. It allows you to make a "shortcut" to a file or directory, so you'd only have to type something like cd my-project.

Answer 5

You can do following:

#!/bin/bash
cd /your/project/directory
# start another shell and replacing the current
exec /bin/bash

EDIT: This could be 'dotted' as well, to prevent creation of subsequent shells.

Example:

. ./previous_script  (with or without the first line)

Answer 6

Jeremy Ruten's idea of using a symlink triggered a thought that hasn't crossed any other answer. Use:

CDPATH=:$HOME/projects

The leading colon is important; it means that if there is a directory 'dir' in the current directory, then 'cd dir' will change to that, rather than hopping off somewhere else. With the value set as shown, you can do:

cd java

and, if there is no sub-directory called java in the current directory, then it will take you directly to $HOME/projects/java - no aliases, no scripts, no dubious execs or dot commands.

My $HOME is /Users/jleffler; my $CDPATH is:

:/Users/jleffler:/Users/jleffler/mail:/Users/jleffler/src:/Users/jleffler/src/perl:/Users/jleffler/src/sqltools:/Users/jleffler/lib:/Users/jleffler/doc:/Users/jleffler/work

Answer 7

to navigate directories quicky, there's $CDPATH, cdargs, and ways to generate aliases automatically

http://jackndempsey.blogspot.com/2008/07/cdargs.html

http://muness.blogspot.com/2008/06/lazy-bash-cd-aliaes.html

http://articles.techrepublic.com.com/5100-10878_11-5827311.html

Answer 8

You can combine an alias and a script:

alias proj='cd \`/usr/bin/proj !*\`"

provided that the script echos the destination path. Note that those are backticks surrounding the script name.

For example, your script could be

#!/bin/bash
echo /home/askgelal/projects/java/$1

The advantage with this technique is that the script could take any number of command line parameters and emit different destinations calculated by possibly complex logic.

Answer 9

the cd is done within the scripts' shell, the shell exits, and then you are left in the directory you were... source the script, don't run it. instead of:

./myscript.sh

do

. ./myscript.sh (notice the dot, space, then script name)