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Shell Script is fun. I love it when I know which commands to use. There are almost thousands of Here is a simple trick to Replace Text and Variables in Files in UNIX. We will use command sed – it is very useful to find and replace text in single or multiple files.

Replace Text in Single File

Replacing hello with hello_world in a single file.

sed -i 's/hello/hello_world/g' somefile.txt
Code language: Arduino (arduino)

Check the arguments

• -i = edit the file “in-place” – sed will directly modify the file if it finds anything to replace
• s = substitute the following text
• hello = what you want to substitute
• hello_world = what you want to replace
• g = global, match all occurrences in the line

Replace Text in Multiple Files

Following command will replace hello with hello_world in multiple files in one go.

sed -i 's/hello/hello_world/g'  *.txt
Code language: Arduino (arduino)

Replace Value of Variable

I had a requirement in shell script to replace value of a variable and use it somewhere. For example: Say variable $path has value “root/user/home” and I need to replace “/” with “-” so that the value looks like “root-user-home”.

${variable//search/replace}
Code language: Arduino (arduino)

• variable – Is name of the variable you want to replace value.
• search – String in variable you want to replace.
• replace – String you want to replace with.