remove all text after a certain character that appears on all odd lines
this works for every line in the file with sed
sed 's/;.*//' how to edit this sed line so it just does all odd lines
2 Answers
With GNU sed:
$ sed '1~2s/;.*//' file The address range 1~2 will match line 1, and then every second line after that. The general case is first~step and the example in the manual is sed -n 1~2p which will print all odd lines.
This is a GNU extension.
The equivalent thing in awk:
$ awk 'NR % 2 { sub(";.*", "") } { print }' file Or, as suggested by Arrow in comments:
$ awk -F';' 'NR % 2 { $0 = $1 } { print }' file which has the same effect, but instead of explicitly substituting out everything after the first ; it uses ; as the field separator (with -F';') and then outputs only the first field (by replacing the whole input line with only the first field for odd rows).
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- @bob Which means that you are not using GNU
sed. What Unix are you on? On BSD systems, GNUsedis sometimes installed asgsed.2017-08-21 14:32:45 +00:00Commented Aug 21, 2017 at 14:32 - 2Maybe a more idiomatic awk:
awk -F\; 'NR%2{$0=$1}1' fileuser232326– user2323262017-08-22 02:03:12 +00:00Commented Aug 22, 2017 at 2:03
This probably might work with all sed version, tested on GNU sed though
$ cat ip.txt foo;bar-baz;xyz a;b;c good bad. hi there d;e cool;hot;normal $ sed 's/;.*//;n' ip.txt foo a;b;c good bad. hi there d;e cool The n command will fetch next line but won't change anything, effectively allowing to change only odd lines
With perl
perl -pe 's/;.*// if $.%2' ip.txt where if $.%2 adds condition to perform substitution only if line number is odd
