Shells and export - a quick cheat sheat / guide for beginners

shell-export.sh

# variables

# assuming you're in a file / script...

# set a variable 
$ foo=1

# prove it exists
$ echo foo

# exporting a variable
# an exported variable will be available on the command line
# after you run this file
$ export foo=1

# prove it exists, even outside of the script itself
$ echo foo


# accessing files

$ /     - root of filesystem
$ ~/    - home directory
$ ./    - current directory
$ ../   - up one directory




# running an executable script
# note - export does *not* have an effect when scripts are run this way
# note - often executable scripts don't have a file extension

# create a file with some editor, maybe vi.
# put #!/bin/sh at the top.
$ vi my-script

# change the permissions to be executable
$ chmod u+x my-script

# run it
$ ./my-script




# 'sourcing' a script
# if you run a script this way and use the export keyword,
# variables will become available on the command line
# some sourceable scripts end in .sh or .xxxrc but not all

# create a file with some editor, maybe vi.
# put #!/bin/sh at the top.
$ vi my-script.sh

# all of these ways to run it are equivalent
$ source my-script.sh
$ source ./my-script.sh
$ . my-script.sh
$ . ./my-script.sh

# now you can use foo
$ echo $foo
1