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

Terminal - Short one line while loop that outputs parameterized content from one file to another
while read l; do echo ${l%% *}; done < three-column-list.txt > only-first-column.txt
2010-07-09 03:42:56
User: zed
Functions: echo read
1
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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

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Alternatives

There are 3 alternatives - vote for the best!

Terminal - Alternatives
cut -f 1 three-column.txt > first-column.txt
2010-07-11 10:13:45
User: postrational
Functions: cut
Tags: Text Processing bash extract oneliner while substitution
4
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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?

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awk '{print $1}' < three-column.txt > first-column.txt
2010-07-09 04:00:05
User: infinull
Functions: awk
Tags: Text Processing bash extract oneliner while substitution
3
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Short one line while loop that outputs parameterized content from one file to another
Comments (0) | Add to favourites | Report as malicious
while read col1 col23; do echo $col1; done < three-column.txt > first-column.txt
2010-07-09 03:59:20
User: infinull
Functions: echo read
Tags: Text Processing bash extract oneliner while substitution
-5
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Short one line while loop that outputs parameterized content from one file to another
Comments (0) | Add to favourites | Report as malicious

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