#!/bin/bash ## # Test files... ## cat <<-'EOF' > file_out_of_date_version__value_modified_inplace some text firmware_version 12.3 # This comment is preserved some more text ... EOF cat <<-'EOF' > file_missing_version__value_appended_to_end some text some more text ... EOF cat <<-'EOF' > file_empty EOF cat <<-'EOF' > file_tiny_edge_case__see_if_output_works_for_you some text [ Support Matrix ] firmware_version | 12.* # this line is corrupted, but why would your configuration look like this in the first place? other_data | "foo" # actual settings firmware_version 12.3 some more text ... EOF for f in file_does_not_exist file*; do touch "$f" awk -i inplace \ -v 'k=firmware_version' \ -v 'v=12.4' \ '$1 == k{f=1;$2=v} 1; ENDFILE {if(!f) print k, v}' "$f" done tail -n +1 file*