How to shorted the middle field of text without losing the other fields

Question

Sorry if this has already been covered. I failed to find anything that fit.

If I have a text file with fields of variable length, how can I truncate one field without sacrificing the other fields? An example;

firstField secondfieldisthislong thirdField
firstField secondfieldisreallylongandgoesonforever thirdField
firstField secondshortfield thirdField

I'd like to truncate the second field to a fixed length. Cut doesn't seem to be able to do this, and my awk/sed skill aren't great. Thanks.

Answer 1

With awk:

awk '{$2 = substr($2, 1, 10)}; 1' file.txt

replace 10 with the length of characters you want.

here we are rebuilding the record(s) with the second field truncated to desired length.

substr($2, offset, length) will do string slicing, starting from offset upto length characters.

Example:

% cat file.txt                              
firstField secondfieldisthislong thirdField
firstField secondfieldisreallylongandgoesonforever thirdField
firstField secondshortfield thirdField

% awk '{$2 = substr($2, 1, 6)}; 1' file.txt
firstField second thirdField
firstField second thirdField
firstField second thirdField

% awk '{$2 = substr($2, 1, 10)}; 1' file.txt
firstField secondfiel thirdField
firstField secondfiel thirdField
firstField secondshor thirdField