Question

I have a file with thousands of lines. I’m looking for help to modify multiple lines which i were to choose.

Package: com.xyz.abc
Version: 1.0
Filename: ./debs/abc.deb

Package: com.xyz.def
Version: 1.0.0-1
Filename: ./debs/def.deb

I need a bash command to detect “Filename” then change them to something like this:

Package: com.xyz.abc
Version: 1.0
Filename: ./debs/download.php?p=abc

Package: com.xyz.def
Version: 1.0.0-1
Filename: ./debs/download.php?p=def

And it will loop till all “Filename” have been changed.

Answer 1

This is a job for sed! From the GNU sed homepage:

Sed is typically used for extracting part of a file using pattern matching or substituting multiple occurrences of a string within a file.

Here is how you could do it:

sed '/^Filename:/s!\(./debs/\)\(.*\).deb!\1download.php?p=\2!' /path/to/input > /path/to/output

Where:

• /^Filename:/ looks for lines starting with (^) the text ‘Filename:’
• s!search!replace! replaces ‘search’ with ‘replace’ where ‘search’ is a regular expression
• \1 is the string captured by the first matching group “\(...\)“
• \2 is the string captured by the second matching group “\(...\)“

Demonstration:

$ echo 'Package: com.xyz.abc
Version: 1.0
Filename: ./debs/abc.deb

Package: com.xyz.def
Version: 1.0.0-1
Filename: ./debs/def.deb' | sed '/^Filename:/s!\(./debs/\)\(.*\).deb!\1download.php?p=\2!' 
Package: com.xyz.abc
Version: 1.0
Filename: ./debs/download.php?p=abc

Package: com.xyz.def
Version: 1.0.0-1
Filename: ./debs/download.php?p=def

For tweaking this and for writing your own sed scripts, please consult the online documentation.