[SOLVED] How to match the beginning of a line with patterns from id file?

Issue

I want to use my id_file to search my big_file extracting lines that match the id at the beginning of the line in big_file.

I'm a beginner and I'm struggling with grep (version grep (BSD grep) 2.5.1-FreeBSD) and understanding the solutions as cited below.

My id_file contains id's:

67b
84D
118
136
166

My big_file looks something like this:

118 ABL1_BCR
118 AC005258
166 HSP90AB1
166 IKZF2_SP
166 IL1RAP_D
136 ABL1_BCR
136 ABL1_BCR
555 BCR_136
555 BCR_136
555 BCR_136
59  UNC45B_M 166
59  WASF2_GN 166
59  YPEL5_CX 166

As suggested by Chris Seymour here

Try 1: I used

grep -wFf id_file big_file

That didn't work obviously, as the numbers occur elsewhere in the lines of the big_file.

Try 2: I modified the id_file;

^67b
^84D
^118
^136
^166

And ran grep -wFf id_file big_file again.

Of course, that didn't work either

I looked at batimar's take here but I'm failing to implement the suggestion.

Better usage is taking only some patterns from some file and this patterns use for your file

grep '^PAT' patterns.txt | grep -f - myfile

This will take all patterns from file patterns.txt starting with PAT and use this patterns from the next grep to search in myfile.

I tried to reproduce the code above with my example in several ways but apparently I just don't get what they mean there as none of it worked.

There were 2 outcomes to my tinkering 1: No such file or directory or no output at all.

Is there even a way to do this with grep only?

I'd greatly appreciate if anyone was able to break it down for me.

Solution

This seems to be an issue with BSD grep. See https://unix.stackexchange.com/questions/352977/why-does-this-bsd-grep-result-differ-from-gnu-grep for similar issues.

You can use awk as an alternate (there's probably a duplicate somewhere with this exact solution):

awk 'NR==FNR{a[$1]; next} $1 in a' id_file large_file

• NR==FNR{a[$1]; next} builds an associative array with first field of id_file as keys
• $1 in a will be true if first field of a line from large_file matches any of the keys in array a. If so, entire line will be printed.

Answered By - Sundeep

Answer Checked By - Pedro (WPSolving Volunteer)