General Information

Review of common shell scripting syntax.

General bash script layout

#!/bin/bash
 
echo "Hello world"
exit 0

Sending and parsing arguments to scripts.

#!/bin/bash
 
echo "The first argument is: $1"
echo "The second argument is: $2"
 
echo "There are $# total arguments."
echo "All of the arguments are: $@"
 
# Loop through arguments one at a time
for myarg in $@; do
  echo "Argument is: $myarg"
done

User input with the read command

#!/bin/bash
 
# If there is no argument passed, prompt for input
if [ -z $1 ]; then
  echo "Enter something: "
  read myname
else
  # There is an argument, use that
  myname=$1
fi
 
echo "You entered: $myname"
exit 0

If/else conditional testing

if [ -f $1 ]; then
  echo "Argument is a file"
elif [ -d $1 ]; then
  echo "Argument is a directory"
else
  echo "Argument is something else..."
fi
 
exit 0

Logical operators

# Logical AND: If first command is true, execute second command
[ -f $1 ] && echo "This is a file"
 
# Logical OR: If first command is true, do not execute second command
[ -f $1 ] || echo "This is not a file"