unix find and replace characters with strings for multiple characters

Question

I want to replace all occurrences of certain characters in my file with words. My question is, can I do that for all the characters using a single command. I am using the following command for replacing every occurrence of 'a' with 'apples'

sed 's/a/apple/g' sample.txt

I don't want to write 3 or 4 similar commands to replace every occurrence of 'b', 'c', 'd' with some words. Is there any way out to extend the above command to suit my need or do I need to use the same three times ?

Be careful when you get to replacing the e characters as it will affect the e in apple as well. You may want to investigate the Regexp features of sed, especially the "word boundary" characters. — Intermernet
– Intermernet, Commented May 22, 2013 at 4:34
@Intermernet What do you suggest I do in that case? I also noticed that using the command I mentioned, I get a replaced output in my terminal but the file contents are not modified. — noobcoder
– noobcoder, Commented May 22, 2013 at 4:37
Check out sed -i. It should allow in-place modification but is sometimes dangerous! copy the file first! — Intermernet
– Intermernet, Commented May 22, 2013 at 4:40

anubhava · Accepted Answer · 2013-05-22 04:37:31Z

3

You can use -e switch in sed to input multiple commands like this:

sed -i.bak -e 's/a/apple/g' -e 's/b/bat/g' -e 's/c/cat/g'

answered May 22, 2013 at 4:37

anubhava

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6 Comments

noobcoder Over a year ago

This sounds good. But does it actually modify the contents of the file or does this simply display it on the terminal ? Using the sed command for me simply displays the changes in the terminal but When I open the file, I see the old unmodified contents

anubhava Over a year ago

I have added -i.bak flag to enable inline editing, this will save the changes in the file itself.

noobcoder Over a year ago

This worked perfectly. However, does the .bak serve as a backup file? If so, when is it actually useful ? Can't I simply use sed -i -e 's/a/apple/g' and so on ?

anubhava Over a year ago

.bak keeps the original content of your file which is for safety measures if anything goes wrong then you can get the original file.

noobcoder Over a year ago

I get it. Now I get the logic.

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