274

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?

Jay LaCroix
  • 2,761

5 Answers5

358

All you should need to do is add a \(backslash) 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)

  1. 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

unrealapex
  • 167
nerdwaller
  • 18,014
28

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 
    /
)
# the quotes are needed to preserve params with spaces
tar "${PARAMS[@]}"
Community
  • 1
Axel Heider
  • 380
28

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 \
/
Paul
  • 61,193
14

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 \
    /
Alter Lagos
  • 252
5

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
timkay
  • 151