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.

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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]\+$'

Answer 5

Using AWK alone:

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

Answer 6

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