====== BASH - Files - Replace all occurrences of string within a file ======

===== Using awk =====

Find and replace "dog" or "cat" or "bird" with "pet" on every line and print it out.

<code bash>
awk '{gsub(/dog|cat|bird,"pet");print}' filename
</code>


Find and replace "dog" with "cat" in every file with extension txt.

<code bash>
awk '{gsub("dog", "cat", $0); print > FILENAME}' *.txt
</code>


Find cat by itself on it's own line even if there are spaces or tabs before it or after it.  Replace it with dog.  Then print the line.

<code bash>
awk '{sub(/^[ \t]*cat .*$/,"dog");print}' filename
</code>


Substitute "dog" with "cat" on lines that don't contain the word "pet".

<code bash>
awk '!/pet/{gsub(/dog/, "cat")};{print}' filename
</code>

----

===== Using sed =====

Change all references of the word dog to cat in the file:

<code bash>
sed -e 's/dog/cat/g' filename
</code>

This uses **sed** to stream edit files, which means change them on the fly.


Find every line that begins with cat.  In that line replace furry with nothing.  Change the file called filename inline (-i).

<code bash>
sed -i '/^cat/{s/furry//}' filename
</code>



Find any line starting with the defined shell variable SHELLVAR (notice ' ' around it so it's evaluated).  When the line is found substitute in foo or boo or coo with bar. Edit the file inline.

<code bash>
sed -i '/^'${SHELLVAR}'/s/\(foo\|boo\|coo\)/bar/' filename
</code>



Replace spaces in a file with hyphens

<code bash>
sed -i 's/ /-/g' *
</code>