Line breaking in bash script

Question

In my company style guide it says that bash scripts cannot be longer than 80 lines. So I have this gigantic sed substitution over twice as long. How can I break it into more lines so that it still works? I have

sed -i s/AAAAA...AAA/BBBBB...BBB/g

And I want something like

sed -i s/AAAAA...AAA/
BBBBB...BBB/g

still having the same effect.

@jordanm If you're over 80 columns long in a bash script, 99% of the time you're doing something wrong. — Swiss
– Swiss, Commented Aug 7, 2012 at 1:47
@jordanm You description sounds like it could possibly be cleaned up. Awk is a scripting language, so complicated Awk scripts are better put in their own file as is done with Perl scripts. More importantly, you can break a command with pipes up into multiple lines without even needing to escape the newline. — Swiss
– Swiss, Commented Aug 7, 2012 at 3:59

Swiss · Accepted Answer · 2012-08-07 01:52:36Z

8

Possible ways to clean up

1) Put your sed script into a file

sed -f script [file ...]

2) Use Regex shorthand

sed 's!A\{30,\}!BBBBB...BBBB!g'

3) Use Bash variables to help break it up a bit

regex="AAAA.AAAAAA"
replace="BBBB...BBBBBBB"
sed "s/${regex}/${replace}/g"

What not to do

1) Escape the newline to break it up into multiple lines.

You will end up with a newline in your sed script that you don't want.

sed 's/THIS IS WRONG /\
AND WILL BREAK YOUR SCRIPT/g'

edited Aug 7, 2012 at 1:52

answered Aug 7, 2012 at 1:44

Swiss

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1 Comment

Burhan Khalid Over a year ago

+1 Yeap, this is the right way; especially with sed in the context of scripts.

Burhan Khalid · Accepted Answer · 2012-08-07 01:38:34Z

1

Use the shell continuation character, which is normally \.

[~]$ foo \
> and \
> bar

Space is not required:

[~]$ foo\
> and\
> bar\
> zoo\
> no space\
> whee!\

answered Aug 7, 2012 at 1:38

Burhan Khalid

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1 Comment

siemanko Over a year ago

yes but that requires space to be inserted before it is used. I do not have this luxury with sed substitution :(

Alexander Putilin · Accepted Answer · 2012-08-07 01:38:48Z

1

Just insert backslash character before a newline:

sed -i s/AAAAA...AAA/\
BBBBB...BBB/g

answered Aug 7, 2012 at 1:38

Alexander Putilin

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2 Comments

siemanko Over a year ago

yes but that requires space to be inserted before it is used. I do not have this luxury with sed substitution :(

Alexander Putilin Over a year ago

Works for me without any spaces.

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