Parse string with bash and extract number

Question

I've got supervisor's status output, looking like this.

frontend                         RUNNING    pid 16652, uptime 2:11:17
nginx                            RUNNING    pid 16651, uptime 2:11:17
redis                            RUNNING    pid 16607, uptime 2:11:32

I need to extract nginx's PID. I've done it via grep -P command, but on remote machine grep is build without perl regular expression support.

Looks like sed or awk is exactly what I need, but I don't familiar with them.

Please help me to find a way how to do it, thanks in advance.

score 24 · Accepted Answer · answered Jun 15 '10 at 13:27

24

sed 's/.*pid \([0-9]*\).*/\1/'

answered Jun 15 '10 at 13:27

reko_t

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In order for this to work you'll need to specify the option to enable extended regular expressions. This is usually '-r' (GNU sed) or '-E' (BSD sed). See: https://stackoverflow.com/questions/16637799/sed-error-invalid-reference-1-on-s-commands-rhs – Joey J Apr 03 '19 at 20:43

score 8 · Answer 2 · answered Jun 15 '10 at 13:46

8

Using AWK alone:

awk -F'[ ,]+' '{print $4}' inputfile

answered Jun 15 '10 at 13:46

Dennis Williamson

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Works great with a pipe: `$ status |grep nginx |awk -F'[ ,]+' '{print $4}' -` – ki9 Aug 29 '16 at 09:57
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@Keith: It's not necessary to pipe `grep` into `awk`. AWK can do it all by itself: `status | awk -F'[ ,]+' '/nginx/ {print $4}'` – Dennis Williamson Aug 29 '16 at 15:51

score 7 · Answer 3 · answered Jun 15 '10 at 13:24

7

$ cat $your_output | sed -s 's/.*pid \([0-9]\+\),.*/\1/'
16652
16651
16607

answered Jun 15 '10 at 13:24

Stephen

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This is known as a UUOC (Useless use of cat) – mikerobi Jun 15 '10 at 13:59
1

@mikerobi : that was just an example of how to pipe stuff into the command... he didn't say how he had his output... but whatever. – Stephen Jun 15 '10 at 14:05

score 6 · Answer 4 · answered Jun 15 '10 at 13:27

6

Solution with awk and cut

vinko@parrot:~$ cat test
frontend                         RUNNING    pid 16652, uptime 2:11:17
nginx                            RUNNING    pid 16651, uptime 2:11:17
redis                            RUNNING    pid 16607, uptime 2:11:32
vinko@parrot:~$ awk '{print $4}' test | cut -d, -f 1
16652
16651
16607

for nginx only:

vinko@parrot:~$ grep nginx test | awk '{print $4}' | cut -d, -f 1
16651

answered Jun 15 '10 at 13:27

Vinko Vrsalovic

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there's no need to use awk + cut + grep. Just awk will do the job. `awk -F"," '/nginx/{print $1}' file` – ghostdog74 Jun 18 '10 at 14:05
@ghostdog74: your command outputs "nginx RUNNING pid 16651". The correct awk only solution is in the answer by Dennis (http://stackoverflow.com/questions/3045493/parse-string-with-bash-and-extract-number/3045718#3045718), using -F '[ ,]+' instead of -F ',' – Vinko Vrsalovic Jun 18 '10 at 19:07
@vinko, its either that, or just use gsub() to get rid of the comma for awk versions that does not support multiple field delimiters. I am just highlighting the point that awk can do the job and there's no need to use other tools. – ghostdog74 Jun 19 '10 at 15:58
@ghostdog74: Right, you can do it with awk only. – Vinko Vrsalovic Jun 19 '10 at 19:29

score 2 · Answer 5 · answered Jun 16 '10 at 02:32

2

Take a look at pgrep, a variant of grep specially tailored for grepping process tabless.

answered Jun 16 '10 at 02:32

Ether

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score 1 · Answer 6 · answered Jun 15 '10 at 13:51

1

assuming that the grep implementation supports the -o option, you could use two greps:

output \
  | grep -o '^nginx[[:space:]]\+[[:upper:]]\+[[:space:]]\+pid [0-9]\+' \
  | grep -o '[0-9]\+$'

answered Jun 15 '10 at 13:51

intuited

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Parse string with bash and extract number

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