Question

for instance,

in bash when i type ps -wef I will get:

UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 20:06 ?        00:00:01 /sbin/init
root         2     0  0 20:06 ?        00:00:00 [kthreadd]
root         3     2  0 20:06 ?        00:00:00 [ksoftirqd/0]
root         6     2  0 20:06 ?        00:00:00 [migration/0]
root         7     2  0 20:06 ?        00:00:02 [watchdog/0]
root         8     2  0 20:06 ?        00:00:00 [cpuset]
root         9     2  0 20:06 ?        00:00:00 [khelper]
root        10     2  0 20:06 ?        00:00:00 [kdevtmpfs]
root        11     2  0 20:06 ?        00:00:00 [netns]
root        12     2  0 20:06 ?        00:00:00 [sync_supers]
root        13     2  0 20:06 ?        00:00:00 [bdi-default]
root        14     2  0 20:06 ?        00:00:00 [kintegrityd]
root        15     2  0 20:06 ?        00:00:00 [kblockd]
root        16     2  0 20:06 ?        00:00:00 [ata_sff]
root        17     2  0 20:06 ?        00:00:00 [khubd]
root        18     2  0 20:06 ?        00:00:00 [md]
root        21     2  0 20:06 ?        00:00:00 [khungtaskd]

and I know which column i want to keep, for example i want to keep the second column which is the PID column, the final result will be:

1 2 3 6 7 8 9 10 11 12 13 14 15 16 17 18 21

the first line of the original result of ps will be deleted.

How can I use sed or awk to get my final result?

Thank you.

Answer 1

 ps -wef | awk 'NR>1 {printf("%s ", $2)}END{printf("\n")'

I hope this helps.,