Need some help with scripting in BASH

allenms · 12-07-2009, 03:02 PM

Need to write a small script that takes a colon-seperated list of items and outputs the items, one per line to standard output without the colons. Thanks,

Al

GrapefruiTgirl · 12-07-2009, 03:03 PM

Hi, welcome to LQ!

You need the `sed` command. It will work perfectly for that task.

Sasha

allenms · 12-07-2009, 03:10 PM

Sasha, appreciate the info but linux is pretty much "greek" to me. Can you give me an example? Just a script that read a small file, and removes the colons : and writes to a second file. Been trying to use the "cut" command but no luck. Thanks,
Al

gerryd · 12-07-2009, 03:12 PM

a sed or awk script would probably be better suited for this task.

gerryd · 12-07-2009, 03:18 PM

check this link out. you can use sed to find and replace characters. http://www.brunolinux.com/02-The_Ter..._with_Sed.html

allenms · 12-07-2009, 03:28 PM

Thanks for the link. Will try to get a handle on this in the AM as it's late on this side of the globe and the old melon needs a rest.

Al

GrapefruiTgirl · 12-07-2009, 04:51 PM

A *very* basic example, to just remove the colons from a file, and put the file back where it was, leaving a backup of the orioginal:

Code:

shell$ sed -i.BAK 's/://g' filename

NOTE: very simple -- but to see other ways of doing this, and other things sed can do, check the man page with:

Code:

shell$ man sed

And, if you need more help, just ask!

Sasha

mehorter · 12-07-2009, 07:11 PM

Code:

sed 's/:/\n/g' filename

This should do what you want.

sed --- calls the sed program.
' --- wrap "code" in single quotes.
s --- substitute command
: --- any ":" matches.
\n --- replace matching ":" with "\n" which is a "new-line" character.
g --- do the command globally; that is, at every occurrence on line.
" filename" ---space then filename.

If this works for you as evidenced by what rolls across your screen then simply redirect your output from the screen to a file like this:

Code:

sed 's/:/\n/g' filename > new_filename

choose a new filename or you will clobber the old one and end up with a zero-byte file or use the -i option, as mentioned above.

alienDog · 12-07-2009, 08:16 PM

sed will work, but you can also do:

Code:

IFS=":"
for ITEM in $@; do
  echo $ITEM
done
unset IFS