How write in my own bash script?

Question

I have a bash script and want to write something in it for use in the next time:

#this get the full path of the script
SCRIPT="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )/$(basename $0)"

NUMBER=10

#This change only in the first occurrence 
cat "$SCRIPT" | sed "1,/NUMBER=../s/NUMBER=../NUMBER=$((NUMBER + 1))/" > "$SCRIPT"

The problem I am having is that it produce an empty file. Can I overwrite my bash script in your own code?

Please see BashFAQ/028.

Dennis Williamson
– Dennis Williamson

2012-05-24 04:04:08 +00:00
Commented May 24, 2012 at 4:04 — Dennis Williamson
– Dennis Williamson, Commented May 24, 2012 at 4:04

Ignacio Vazquez-Abrams · Accepted Answer · 2012-05-23 17:21:40Z

4

cat "$SCRIPT" | ... > "$SCRIPT"

Don't do this. It will only lead to pain and suffering. And don't write self-modifying code at all if you can help it. But if you must, write to a temporary file first and rename after.

answered May 23, 2012 at 17:21

Ignacio Vazquez-Abrams

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Comments

tripleee · Accepted Answer · 2012-05-23 17:34:08Z

1

Using temp file can save the situation:

#this get the full path of the script
SCRIPT="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )/$(basename $0)"

NUMBER=10

#This change only in the first occurrence 
sed "1,/NUMBER=../s/NUMBER=../NUMBER=$((NUMBER + 1))/" "$SCRIPT" > temp.tmp
cat temp.tmp > "$SCRIPT"
rm temp.tmp

But it's really interesting if there's a way to solve the problem without temp file:)

edited May 23, 2012 at 17:34

tripleee

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answered May 23, 2012 at 17:29

dmchmk

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4 Comments

a3nm Over a year ago

cat "$SCRIPT" | sed "1,/NUMBER=../s/NUMBER=../NUMBER=$((NUMBER + 1))/" | sponge "$SCRIPT" (command sponge from moreutils)

Dennis Williamson Over a year ago

All these Useless Uses of Cats!

a3nm Over a year ago

Right, you don't need the invocation of cat. Sorry for that.

dmchmk Over a year ago

It's not our's, it was copied from the topicstarter's message:)

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