remove comma from last line

Question

How do I remove the comma from the last line of the file? Here is the file:

# cat ox_data_archive_r_20120727.json
{\"name\": \"secondary_ua\",\"type\":\"STRI         


        

Answer 1

This should work:

sed '$ s/,$//g' input_file

• The first $ selects the last line.

You could add -i and sed will apply the changes to your input_file.

Answer 2

The awk answer is certainly more verbose than the sed:

awk 'NR>1 {print prev} {prev=$0} END {sub(/,$/,"", prev); print prev}' file

Answer 3

$ cat input.txt
{"name": "secondary_ua","type":"STRING"},
{"name": "request_ip","type":"STRING"},
{"name": "cb","type":"STRING"},
$ sed '$s/,$//' < input.txt
{"name": "secondary_ua","type":"STRING"},
{"name": "request_ip","type":"STRING"},
{"name": "cb","type":"STRING"}

From the documentation of GNU sed:

$: This address matches the last line of the last file of input, or the last line of each file when the -i or -s options are specified.