How do you grep in a script?
The grep command searches through the file, looking for matches to the pattern specified. To use it type grep , then the pattern we’re searching for and finally the name of the file (or files) we’re searching in. The output is the three lines in the file that contain the letters ‘not’.
Can we use grep in shell script?
How can I use grep to find an exact word inside of a file entered by the user as string. Try using -F option. Type man grep on shell for more details. It’s recommended to enclose search string and file name with quotes to avoid unexpected output because of white spaces.
How to get output and return value of grep?
The response can be no lines, 1 line, or 2 lines. In case grep returns no lines (grep return code 1), I abort the script; if I get 1 line I invoke A () or B () if more than 1 line. grep’s return code is 0 when the output is 1-2 lines. grep has return value (0 or 1) and output. How can I catch them both ? If I do something like:
What is the return code of grep in Bash?
The response can be no lines, 1 line, or 2 lines. In case grep returns no lines (grep return code 1), I abort the script; if I get 1 line I invoke A () or B () if more than 1 line. grep’s return code is 0 when the output is 1-2 lines. grep has return value (0 or 1) and output.
When to use grep with uncorrelated output?
This approach is useful in situations where the output of the command and its return code (a.k.a. exit status) are uncorrelated. But, for grep, they are highly correlated: If it produced output, it succeeded. If it didn’t produce output, it failed.
Can you use the-C flag in grep?
If you need the result of grep, you can not use the -c flag as outlined in the other answer. What you can do, though, is running twice, once with -c flag to get the number of matches and one without -c flag, to see the matches. However, this can be very inefficient, depending on the size of your input file.