bash script

Steps to create a bash script executable and run it

1. Create file with .sh extension, e.g. with touch filename.sh
2. Write contents of your script (see below)
3. Make it executable: chmod +x filename.sh
4. Move file into folder ~/bin or equivalently $HOME/bin

5. Check whether the ~/bin folder is in your path and add it if necessary

   • I put my own shell scripts into the folder ~/bin.
   • To check whether the folder ~/bin is in your system’s PATH, run echo $PATH.

   • If you don’t see ~/bin in there (e.g. something:~/bin:something-else) add it to the end of your PATH via

     export PATH=$PATH:~/bin

   • Open a new shell tab so that the new PATH is active.
   • You can now run the script executable with $ filename

6. Optional:

   1. Add alias myScriptName='./filename.sh' to .bash_profile
   2. Reload shell or run . .bash_profile

   3. Call your new shell script by just typing

      myScriptName

My first shell script - step by step

1. Write a program

   • First line is #!/bin/bash (bash shell) or #!/bin/sh (sh shell)
   • Then write your code below, e.g.

   #!/bin/bash
   # My first script
   
   echo "Hello World!"

2. Save it as my_script

3. Setting permissions - in order to make the script executable

   chmod 755 my_script

4. Run the script

   ./my_script

5. Put script into the folder /Users/myName/bin to make it executable from anywhere because hopefully /Users/myName/bin is already in the path.

Example and instructions taken and adapted from http://linuxcommand.org/wss0010.php

Recipe to write a basic shell script

Example 1

#!/bin/bash -l

export LANG=en_US.UTF-8

-l: Use currently logged-in user

Example 2

This example contains an if-then clause.

# test if the current commit already has a tag
has_tag=$( git describe --tags --exact-match --match=builds/$PLATFORM/* HEAD || echo false )

if $FORCE || [ "$has_tag" == "false" ]
then
# proceed with build
  exit 0
else
# nothing changed
  exit 1
fi

Links

• See the Wikipedia article for more examples.
• How do I parse command line arguments in bash?