Shell Programming and Scripting

Originally Posted by durden_tyler

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As for why it doesn't work the way it looks - you have two different processes (a) a read process and (b) a write process, both sharing the same resource - your file. When they are executed by the OS, a race condition occurs between them which renders the final output unpredictable.
If the writing is done before the reading, you get a zero-byte file. If the writing is done mid-way during the reading process, you may get a "half-baked" output file. The safest way, therefore, is to either use a temporary file explicitly or let sed do it via the "-i" modifier - which is not available in all sed versions.
You could also use other tools - Bash, awk, Perl etc. but the temporary file will be involved, either explicitly or implicitly.

Originally Posted by RavinderSingh13

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That tr command worked for me. Also && condition will make sure like first reading of Input_file and it's output's redirection is done then only it will go to next command which is mv temp_Input_file Input_file, ideally it shouldn't fail. Kindly do let me know your views on same.
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