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Bash - Script Stub

Where I was previously employed, we had an ace programmer who knew a bunch of languages. He was also the go-to guy when you had questions on how to accomplish something with a script. He finally created a little stub, a files full of scripting examples that you could just strip out and edit as needed. Eventually, I got good enough at these routines that I didn't have to look at the stub, but it was a good learning tool, and something that others may find useful.

The Actual Stub

The stub is well documented, but keep in mind that this is by no means an exhaustive script! There are a lot more routines that could be added. If you have examples that would fit nicely into this stub, then please feel free to add some changes:

#!/bin/sh

# By exporting the path, this keeps you from having to enter full paths for commands that exist in those paths:

export PATH="$PATH:/bin:/usr/bin:/usr/local/bin"

# Determine and save absolute path to program directory.
# Attention! In bash, the ' 'represents the string itself; But " " is a little different. $, ` `, and \ represent call variable values, reference commands, and escape characters, respectively
# When done will be in same directory as script:

PGM=`basename $0`               # Name of the program
CDIR=`pwd`                  # Save directory program was run from

PDIR=`dirname $0`
cd $PDIR
PDIR=`pwd`

# If a program accepts filenames as arguments, this will put us back where we started.
# (Needed so references to files using relative paths work.):

cd $CDIR

# Use this if script must be run by certain user:

runby="root"
iam=`/usr/bin/id -un`
if [ $iam != "$runby" ]
then
    echo "$PGM : program must be run by user \"$runby\""
    exit
fi

# Check for missing parameter.
# Display usage message and exit if it is missing:

if [ "$1" = "" ]
then
    echo "$PGM : parameter 1 is required"
    echo "Usage: $PGM param-one"
    exit
fi

# Prompt for data (in this case a yes/no response that defaults to "N"):

/bin/echo -n "Do you wish to continue? [y/N] "
read yn
if [ "$yn" != "y" ] && [ "$yn" != "Y" ]
then
    echo "Cancelling..."
    exit;
fi

# If only one copy of your script can run at a time, use this block of code.
# Check for lock file.  If it doesn't exist create it.
# If it does exist, display error message and exit:

LOCKF="/tmp/${PGM}.lock"
if [ ! -e $LOCKF ]
then
    touch $LOCKF
else
    echo "$PGM: cannot continue -- lock file exists"
    echo
    echo "To continue make sure this program is not already running, then delete the"
    echo "lock file:"
    echo
    echo "    rm -f $LOCKF"
    echo
    echo "Aborting..."
    exit 0
fi

script_list=`ls customer/*`

for script in $script_list
do
    if [ $script != $PGM ]
    then
        echo "./${script}"
    fi
done

# Remove the lock file

rm -f $LOCKF

Conclusion

Scripting is a System Administrator's friend. Being able to quickly do certain tasks in a script streamlines process completion. While by no means an exhaustive set of script routines, this stub offers some common usage examples.

Last update: February 18, 2022

Author: Steven Spencer

Contributors: Ezequiel Bruni

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