Linux Bash Script, Single Command But Multiple Lines?

I have the following script I wrote by searching Google, and it backs up my Linux system to an archive:

#!/bin/bash # init DATE=$(date +20%y%m%d) tar -cvpzf /share/Recovery/Snapshots/$HOSTNAME_$DATE.tar.gz --exclude=/proc --exclude=/lost+found --exclude=/sys --exclude=/mnt --exclude=/media --exclude=/dev --exclude=/share/Archive / 

This works, but I am wondering if I can format the script to show the command over multiple lines, something like this, so it is easy to edit later:

tar -cvpzf /share/Recovery/Snapshots/$HOSTNAME_$DATE.tar.gz --exclude=/proc --exclude=/lost+found --exclude=/sys --exclude=/mnt --exclude=/media --exclude=/dev --exclude=/share/Archive / 

That way it is easier to read and edit later. Is it possible to format a Bash script this way?

5 Answers

All you should need to do is add "\" at the end of each line and it should be good to go.

So yours will look like:

tar -cvpzf /share/Recovery/Snapshots/$(hostname)_$(date +%Y%m%d).tar.gz \ --exclude=/proc \ --exclude=/lost+found \ --exclude=/sys \ --exclude=/mnt \ --exclude=/media \ --exclude=/dev \ --exclude=/share/Archive \ / 

A Few Shortcuts

(based on your comment update for setting $HOSTNAME)

$HOSTNAME

Two options to set that:

1. Set HOSTNAME

   HOSTNAME=$(hostname)

2. Use command substitution (e.g. $(command))

   So it would look like above. That just makes the command run before using it.

$DATE

Another variable avoided would be easily:

$(hostname)_$(date +%Y%m%d).tar.gz \ 

$ man date will have the formats for the date options, the above is YYYYmmdd

Use the backslash to continue a command on the next line:

tar -cvpzf /share/Recovery/Snapshots/$HOSTNAME_$DATE.tar.gz \ --exclude=/proc \ --exclude=/lost+found \ --exclude=/sys \ --exclude=/mnt \ --exclude=/media \ --exclude=/dev \ --exclude=/share/Archive \ / 

You can use this in bash

PARAMS=( -cvpzf /share/Recovery/Snapshots/$HOSTNAME_$DATE.tar.gz --exclude=`enter code here`/proc --exclude=/lost+found --exclude=/sys --exclude=/mnt # this is a comment --exclude=/media --exclude=/dev # --exclude=/something --exclude=/share/Archive / ) tar ${PARAMS[@]} 

The same command, but with comments for each line, would be:

tar -cvpzf /share/Recovery/Snapshots/$(hostname)_$(date +%Y%m%d).tar.gz `#first comment` \ --exclude=/proc `#second comment` \ --exclude=/lost+found `# and so on...` \ --exclude=/sys \ --exclude=/mnt \ --exclude=/media \ --exclude=/dev \ --exclude=/share/Archive \ / 

Axel Heider provided a good alternative to backslashes. Two notes:

1. The command can be included in the list, and
2. The use of the list should be in double quotes "${PARAMS[@]}", so that any spaces in parameters get preserved.

 #!/bin/bash params=( show hello, world "multi word" ) function show { echo --- Showing \""$@"\" as parameters --- for i in "$@"; do echo i=$i done } ${params[@]} "${params[@]}" 

outputs

 $ bash test.sh --- Showing "hello, world multi word" as parameters --- i=hello, i=world i=multi i=word --- Showing "hello, world multi word" as parameters --- i=hello, i=world i=multi word