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I am new to linux, I have one 200 lines in a file. In that file I need to replace the specific word eg: existing word: foo New word : bar I read some blogs...i understood it can be done with sed. But I do not know how to do that with a shell script

sed 's/foo/bar/' /path to a file

I need to write a script, I do not know how to give the file as an input or should I store in a variable and change the specific word.

The script should change the specific word as well as the file name eg: Input File name: cat home.txt (word to be replaced -->cat) OutPut Filename: Dog home.txt(Cat should be replaced with Dog)

Kindly help!

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  • May the file also contain the string foo as a substring of a word that should not be modified, for example food, foobar or my-foo? Commented Mar 19, 2020 at 8:04
  • sed can read from standard input or take a filename as argument. These work: sed 's/foo/bar/' < "file" or sed 's/foo/bar' "file". Commented Mar 19, 2020 at 8:23
  • @Kusalananda No the file doesn't contain substring...its only foo..sed command should reolace the exact word..and it should be case senstitive Commented Mar 19, 2020 at 8:38
  • @Devon yes , it works like giving the file as an input, but in my case i need to replace in case senstitive...how can i do it with sed Commented Mar 19, 2020 at 8:41
  • Do you plan on editing the file in-place? Doing it in a script is no different than doing it on the command line. Commented Mar 19, 2020 at 8:56

1 Answer 1

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If you want to change the string foo with bar then you could use this:

#!/bin/bash # the pattern we want to search for search="foo" # the pattern we want to replace our search pattern with replace="bar" # my file my_file="/path/to/file" # generate a new file name if our search-pattern is contained in the filename my_new_file="$(echo ${my_file} | sed "s/${search}/${replace}/")" # replace all occurrences of our search pattern with the replace pattern sed -i "s/${search}/${replace}/g" "${my_file}" # rename the file to the new filename mv "${my_file}" "${my_new_file}"

Please be aware that if the search pattern matches parts of a word those parts are also substituted e.g.:

"I have a caterpillar."

with a search string of "cat" and a replace string of "dog", would become

"I have a dogerpillar."

Avoiding this a unfortunately not fully trivial.

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  • Thank u for your answer...Is it possible to make case sensitive? foo -->bar Foo--Bar Commented Mar 19, 2020 at 12:51
  • am getting the error while reneming the file "No such file or directory" Can u pls help me Commented Mar 19, 2020 at 13:36
  • When you are adding the -x flag to the first line of the script (#!/bin/bash -x ) then you are able to see which commands are executed. This should give you a hint about the problem. Commented Mar 19, 2020 at 13:55
  • thank u....Could you please help me with the case senstitive... For eg: In the same command sed should be able to replace both small and caps Commented Mar 19, 2020 at 13:57
  • for eg: foo -- >bar Foo -->Bar. How to do that Commented Mar 19, 2020 at 13:57

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