unix – Page 4 – Kev's Development Toolbox

May 21, 2016

Inline text replacement with sed

Replacing values in files is incredibly easy with sed. Here’s some examples:

sed 's/match/replace/g' file.txt

Find match, replace with replace, globally (all matches), in file.txt

sed 's/match/replace/g' file.txt > file2.txt

Same as before, but write results to new file, file2.txt

sed -n 's/match/replace/p' file.txt

-n suppresses output of the results, but /p prints out just the matching patterns that are replaced.

sed -i.old 's/match/replace/g' file.txt

Replace matches in the input file with inline replace (-i), renaming original file file.txt.old and writing inline replace results to file.txt

January 17, 2016

Linux shell history

Useful tips:

history – list history of all recorded shell history
history n – list last n statements
!n – execute nth statement from history
!! execute last statement

April 5, 2015

Linux shell command history

List history:

history

Execute prior command:

!n

where n is command listed from history.

July 7, 2014

Combining find and grep

Quick note to remember this syntax as every few months I find a need to do a grep within a number of files:

find -name "pattern" -exec grep "pattern" {} ;

Grep options:
-H print filename in results
-n print line number where match was found
-l limit match to first found match in file (useful if you want to find files containing a match but don’t care how many matches are in each file)

Pipe to wc -l to count file occurrences, eg:

find -name "pattern" -exec grep -l "pattern" {} ; | wc -l

Use egrep if you need to use regex in the pattern.