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I want to test the output of a bash script when one of the executables it depends on is missing, so I want to run that script with the dependency "hidden" but no others. PATH= ./script isn't an option because the script needs to run other executables before it reaches the statement I want to test. Is there a way of "hiding" an executable from a script without altering the filesystem?
For a concrete example, I want to run this script but hide the git executable (which is its main dependency) from it so that I can test its output under these conditions.
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To silence the output of a command, we redirect either stdout or stderr — or both — to /dev/null. To select which stream to redirect, we need to provide the FD number to the redirection operator.
If you are executing a Bash script in your terminal and need to stop it before it exits on its own, you can use the Ctrl + C combination on your keyboard.
Before being able to run your script, you need your script to be executable. In order to make a script executable on Linux, use the “chmod” command and assign “execute” permissions to the file.
Using the stty Command The stty command displays or changes the settings of a terminal and is also useful for hiding user input. We can use the echo setting of the stty command for enabling or disabling the echoing of input characters.
You can use the builtin command, hash:
hash [-r] [-p filename] [-dt] [name]Each time hash is invoked, it remembers the full pathnames of the commands specified as name arguments, so they need not be searched for on subsequent invocations. ... The -p option inhibits the path search, and filename is used as the location of name. ... The -d option causes the shell to forget the remembered location of each name.
By passing a non-existent file to the -p option, it will be as if the command can't be found (although it can still be accessed by the full path). Passing -d undoes the effect.
$ hash -p /dev/null/git git
$ git --version
bash: /dev/null/git: command not found
$ /usr/bin/git --version
git version 1.9.5
$ hash -d git
$ git --version
git version 1.9.5
Add a function named git
git() { false; }
That will "hide" the git command
To copy @npostavs's idea, you can still get to the "real" git with the command builtin:
command git --version
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