In-place processing with grep

Question

I\'ve got a script that calls grep to process a text file. Currently I am doing something like this.

$ grep \'SomeRegEx\' myfile.txt > myfile.txt.temp
$ m         


        

Answer 1

To edit file in-place using vim-way, try:

$ ex -s +'%!grep foo' -cxa myfile.txt

Alternatively use sed or gawk.

Answer 2

sponge (in moreutils package in Debian/Ubuntu) reads input till EOF and writes it into file, so you can grep file and write it back to itself.

Like this:

grep 'pattern' file | sponge file

Answer 3

Perl has the -i switch, so does sed and Ruby

sed -i.bak -n '/SomeRegex/p' file

ruby -i.bak -ne 'print if /SomeRegex/' file

But note that all it ever does is creating "temp" files at the back end which you think you don't see, that's all.

Other ways, besides grep

awk

awk '/someRegex/' file > t && mv t file

bash

while read -r line;do case "$line" in *someregex*) echo "$line";;esac;done <file > t && mv t file