Shell scripting tutorial

From Linuxintro
Revision as of 00:21, 2 January 2012 by imported>ThorstenStaerk (→‎line feeds)

This is a tutorial for bash shell scripting.

Hello world

echo "hello world"
#!/bin/bash
echo "hello world"

input

echo "what is your name? "
read name
echo "hello $name"

Note that the variable is called $name, however the correct statement to read it is

read name

It is a common mistake to write

read $name

which means "read a string and store it into the variable whose name is stored in $name"

conditions

echo "what is your name? "
read name
if [ $name = "Thorsten" ]; then echo "I know you"

common mistakes

Common mistakes are:

line feeds

Let's look at the following script:

read name
if [ $name = "Thorsten" ]; then echo "I know you"

Instead of a semicolon you can write a line feed like this:

read name
if [ $name = "Thorsten" ]
  then echo "I know you"

And instead of a line feed you can use a semicolon:

read name; if [ $name = "Thorsten" ]; then echo "I know you"

If you want to insert a line feed where you do not need one, e.g. to make the code better readable, you must prepend it with a backslash:

read \
  name
if [ $name = "Thorsten" ]
  then \
    echo "I know you"

calling commands

Calling commands in a bash script is as easy as it can be: You just write the command to be called, like this:

echo "Now calling a browser"
firefox
echo "Continuing with the script"

See also