Short one line while loop that outputs parameterized content from one file to another

while read col1 col23; do echo $col1; done < three-column.txt > first-column.txt

-5

By: infinull

2010-07-09 03:59:20

echo read Text Processing bash extract oneliner while substitution

3 Alternatives + Submit Alt

Short one line while loop that outputs parameterized content from one file to another
This is sample output - yours may be different.
4

awk '{print $1}' < three-column.txt > first-column.txt

infinull · 2010-07-09 04:00:05 7
Short one line while loop that outputs parameterized content from one file to another

There is a common command for outputting a field or list of fields from each line in a file. Why wouldn't you just use cut?
This is sample output - yours may be different.
4

cut -f 1 three-column.txt > first-column.txt

postrational · 2010-07-11 10:13:45 7
Short one line while loop that outputs parameterized content from one file to another

The above is an example of grabbing only the first column. You can define the start and end points specifically by chacater position using the following command: while read l; do echo ${l:10:40}; done < three-column-list.txt > column-c10-c40.txt Of course, it doesn't have to be a column, or extraction, it can be replacement while read l; do echo ${l/foo/bar}; done < list-with-foo.txt > list-with-bar.txt Read more about parameter expansion here: http://wiki.bash-hackers.org/syntax/pe Think of this as an alternative to awk or sed for file operations
This is sample output - yours may be different.
1

while read l; do echo ${l%% *}; done < three-column-list.txt > only-first-column.txt

zed · 2010-07-09 03:42:56 5

What Others Think

rahimhh21 · 110 weeks and 6 days ago

Perfecthomepugs · 101 weeks and 6 days ago

pugpuppies95 · 64 weeks ago

yeneba6574 · 21 weeks and 6 days ago

yeneba6574 · 19 weeks ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

You must be signed in to comment.

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

Share Your Commands

Similar Commands

In place line numbering

Iterate through a file where instead of Newline characters, values are separated with a non-white space character.

Access variables inside a - piped while - loop

It outputs a given line from a file

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for:

» all commands
» commands with 3 up-votes (commandlinefu3)
» commands with 10 up-votes (commandlinefu10)