What is the fastest way to process line by line in bash?

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How to loop over the lines of a file?

Let's say I cat a file and I want to run a bash command on each line and write each line as output.

How can I run a bash command on a single line the most succinct way?

cat something | lineBylineInplpace grep -E "spo" > &1

(I forget the standard descriptor symbol = / )

Should output the output of each line to the new file in place with the line it used for input.

I realize that this is very similar to awk. Is there a bash builtin kind of way to make this faster?

i found http://www.linuxquestions.org/questions/programming-9/bash-shell-script-read-file-line-by-line-136784/page2.html — Tegra Detra, Dec 09 '12 at 22:18
this seems to be the best so far cat file | ( while read line do echo process $line done ) — Tegra Detra, Dec 09 '12 at 22:19
also its not a duplicate i wanted to edit line by line in the file this seems a bit pushy and negative to close this topic. there are a million ways to do things like this and i am sure there are ways that you dont kno this "bash" thing has been around for a while if u didnt know. the problem i think is people really forgot how they used it and i want to kno not get pushed down on the stack — Tegra Detra, Dec 10 '12 at 06:18

Gilles Quénot · Answer 1 · 2012-12-09T22:35:06.337

11

The proper way to process a file line by lines is :

   while read -r line; do
       echo "$line"
    done < /path/to/file.txt

NOTE

edited Dec 09 '12 at 22:35

answered Dec 09 '12 at 22:19

Gilles Quénot

hey thank you nice link that will help a small correction echo "$line" should be echo "$line" >> output =) – Tegra Detra Dec 09 '12 at 22:22
Free free to modify it to fit your needs. =) – Gilles Quénot Dec 09 '12 at 22:36
You missed setting IFS. See How to loop over the lines of a file? and other threads we've already had on this topic. – Gilles 'SO- stop being evil' Dec 09 '12 at 23:09

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