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.

reko_t · Accepted Answer · 2010-06-15 13:27:00Z

26

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

answered Jun 15, 2010 at 13:27

reko_t

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1 Comment

Joey J Over a year ago

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: stackoverflow.com/questions/16637799/…

Stephen · Accepted Answer · 2010-06-15 13:24:30Z

8

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

answered Jun 15, 2010 at 13:24

Stephen

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2 Comments

mikerobi Over a year ago

This is known as a UUOC (Useless use of cat)

Stephen Over a year ago

@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.

Dennis Williamson · Accepted Answer · 2010-06-15 13:46:15Z

8

Using AWK alone:

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

answered Jun 15, 2010 at 13:46

Dennis Williamson

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2 Comments

ki9 Over a year ago

Works great with a pipe: $ status |grep nginx |awk -F'[ ,]+' '{print $4}' -

Dennis Williamson Over a year ago

@Keith: It's not necessary to pipe grep into awk. AWK can do it all by itself: status | awk -F'[ ,]+' '/nginx/ {print $4}'

Vinko Vrsalovic · Accepted Answer · 2010-06-15 13:27:02Z

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, 2010 at 13:27

Vinko Vrsalovic

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4 Comments

ghostdog74 Over a year ago

there's no need to use awk + cut + grep. Just awk will do the job. awk -F"," '/nginx/{print $1}' file

Vinko Vrsalovic Over a year ago

@ghostdog74: your command outputs "nginx RUNNING pid 16651". The correct awk only solution is in the answer by Dennis (stackoverflow.com/questions/3045493/…), using -F '[ ,]+' instead of -F ','

ghostdog74 Over a year ago

@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.

Vinko Vrsalovic Over a year ago

@ghostdog74: Right, you can do it with awk only.

Ether · Accepted Answer · 2010-06-16 02:32:30Z

2

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

answered Jun 16, 2010 at 2:32

Ether

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Comments

intuited · Accepted Answer · 2010-06-15 13:51:54Z

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, 2010 at 13:51

intuited

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