How to iteratively find number of lines between two patterns?-CodePudding

This question is similar, but distinct from 1, 2, and 3.

Instead of pasting the lines in between the two patterns, I want to iteratively count the lines.

For example, given file.txt with these strings

abc
123
daafsd
asdfas
asdcasdfa
123
sdfasdc
asdfasdcasd
asdfasdfasdf
asdfasdfasdf
ascasdcasdcasd
123
asdcasdfacasdcas
123
asdfasdcasdcasc
asadfasdfas
123

I would want to count the lines between the pattern of 123. So, the expected output would be:

Any suggestions?

CodePudding user response：

awk '$0=="123" {if (n) print NR-1-n; n=NR}' file

This uses the line number of matched lines to print the number of lines between them.