how to use fg foreground command? no such job!

IanVaughan · 04-16-2010, 05:55 AM

I have many processes running that printf local debug. (they will log to file later!)

I start them by

Code:

( sleep 20000000 | fp ) &

else they get killed/stop by themselves.

So now its running in the background, I want to bring it to the front to see the printfs.

Code:

# pgrep fp
3301

# fg 3301
-bash: fg: 3301: no such job

Why no such job?!
How do I use it?

man fg

Quote:

fg [jobspec]
Resume jobspec in the foreground, and make it the cur-
rent job. If jobspec is not present, the shellâs
notion of the current job is used. The return value
is that of the command placed into the foreground, or
failure if run when job control is disabled or, when
run with job control enabled, if jobspec does not
specify a valid job or jobspec specifies a job that
was started without job control.

What is jobspec?

Sayan Acharjee · 04-16-2010, 05:58 AM

Quote:

Originally Posted by IanVaughan

I have many processes running that printf local debug. (they will log to file later!)

I start them by

Code:

( sleep 20000000 | fp ) &

else they get killed/stop by themselves.

So now its running in the background, I want to bring it to the front to see the printfs.

Code:

# pgrep fp
3301

# fg 3301
-bash: fg: 3301: no such job

Why no such job?!
How do I use it?

man fg

What is jobspec?

First run the command jobs to know the job id which is different from the process id.
Then use fg to bring it in foreground:

Quote:

#fg job_id

cola · 04-16-2010, 06:06 AM

Quote:

Originally Posted by IanVaughan

I have many processes running that printf local debug. (they will log to file later!)

I start them by

Code:

( sleep 20000000 | fp ) &

else they get killed/stop by themselves.

So now its running in the background, I want to bring it to the front to see the printfs.

Code:

# pgrep fp
3301

# fg 3301
-bash: fg: 3301: no such job

Why no such job?!
How do I use it?

man fg

What is jobspec?

Code:

man jobs

jobs command will display the background process.Then fg <number>

Sergei Steshenko · 04-16-2010, 06:17 AM

Quote:

Originally Posted by cola

...
Then fg <number>

AFAIR it's

Code:

fg %JOB_NUMBER

- at least, this is how it works for me.

A job can also be put into foreground based on its PID using 'kill' with the appropriate signal - see

Code:

man kill
man 7 signal

.

cola · 04-16-2010, 06:37 AM

Quote:

Originally Posted by Sergei Steshenko

AFAIR it's

Code:

fg %JOB_NUMBER

- at least, this is how it works for me.

A job can also be put into foreground based on its PID using 'kill' with the appropriate signal - see

Code:

man kill
man 7 signal

.

Code:

If Python don't have unless construct, it means it doesn't need one. (c) ghostdog74

Why is this?

Sergei Steshenko · 04-16-2010, 07:09 AM

Quote:

Originally Posted by cola

Code:

If Python don't have unless construct, it means it doesn't need one. (c) ghostdog74

Why is this?

I quoted ghostdog74 - ask him

. Perl does have 'unless' construct, and I like it.

IanVaughan · 04-16-2010, 07:15 AM

Can you not post crap thats not related to this topic please!

Anyway, jobs returns nothing for me!

Cheers.

cola · 04-16-2010, 07:19 AM

Quote:

Originally Posted by IanVaughan

Can you not post crap thats not related to this topic please!

Anyway, jobs returns nothing for me!

Cheers.

If jobs does not return anything then there is no background process.

IanVaughan · 04-16-2010, 07:22 AM

Quote:

Originally Posted by cola

If jobs does not return anything then there is no background process.

Interesting!
But I have many processes running, are they actually not all background processes, or just processes then?

What I may be after then is to be able to switch to another process that is running!?

PMP · 04-16-2010, 07:22 AM

What actually this does?

have you tried this on a shell ?

Code:

( sleep 20000000 | fp ) &

do something like

Code:

(sleep 10 | ps ) &

What goes in to background ?

Hope it gives you a pointer.

I personally did not like the word crap for normal discussion

cola · 04-16-2010, 07:29 AM

Quote:

Originally Posted by IanVaughan

Interesting!
But I have many processes running, are they actually not all background processes, or just processes then?

What I may be after then is to be able to switch to another process that is running!?

If you use "&" at the end of a command,then you get a background command.
Example:

Code:

mplayer file1.flv &

IanVaughan · 04-16-2010, 07:34 AM

Quote:

Originally Posted by PMP

What actually this does?

have you tried this on a shell ?

Code:

( sleep 20000000 | fp ) &

do something like

Code:

(sleep 10 | ps ) &

What goes in to background ?

Ok, my mistake, I had killed my "fp" background process!
When started (as quoted above) jobs gives me :-

Code:

[1]+  Running                 ( sleep 20000000 | fp ) &

so, typing in

Code:

fg 1

should bring it to the front, right? I cant prove it right now, but will post back when I can.

And once in the fg, how can I push it back to the bg again?

thanks for bearing with me!

PMP · 04-16-2010, 07:43 AM

Yes your process fp is running at that time.

My question was it in background ?
pgrep will give you the processid, no matter it is in forground or background.

Have you tried what I said

Code:

(sleep 1000 | ps ) &

after doing so you will receive

-bash-3.2$ (sleep 1000 | ps) &
[5] 30766

Job Number, Processid

no if you do

fg 5 ie fg [job_number] you will se your job in background.

tommylovell · 04-16-2010, 08:26 AM

Quote:

Originally Posted by IanVaughan

Ok, my mistake, I had killed my "fp" background process!
When started (as quoted above) jobs gives me :-

Code:

[1]+  Running                 ( sleep 20000000 | fp ) &

so, typing in

Code:

fg 1

should bring it to the front, right? I cant prove it right now, but will post back when I can.

And once in the fg, how can I push it back to the bg again?

thanks for bearing with me!

To bring it to the foreground you need to

Code:

fg %1

To put it in the background you need to

Code:

bg %1

e.g.

Code:

[root@athlonz ~]# ( sleep 20000000 | cat /etc/*ease ) &
[1] 31071
[root@athlonz ~]# Fedora release 10 (Cambridge)
Fedora release 10 (Cambridge)
Fedora release 10 (Cambridge)

[root@athlonz ~]# jobs
[1]+  Running                 ( sleep 20000000 | cat /etc/*ease ) &
[root@athlonz ~]# ( sleep 20000000 | cat /etc/fstab ) &
[2] 31120
[root@athlonz ~]# 
#
# /etc/fstab
# Created by anaconda on Mon Feb 15 02:00:36 2010
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or vol_id(8) for more info
#
UUID=54716048-c91b-4f48-b37e-fb09ce21e412 /     ext3    defaults        1 1
UUID=1fd8498a-868b-46b6-8ced-01155b0c5962 /bkup ext3    defaults        1 2
UUID=97bcf411-5558-4cf9-9aef-5108fa686246 /boot ext3    defaults        1 2
UUID=59d3649f-4c9d-46b2-94c8-b7d29578328e /boot2 ext3   defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
UUID=b827e20f-db5b-47b2-be38-17489895a0ad swap  swap    defaults        0 0
/dev/mapper/vgz01-tommy /home/tommy             ext3    defaults        1 2

[root@athlonz ~]# jobs
[1]-  Running                 ( sleep 20000000 | cat /etc/*ease ) &
[2]+  Running                 ( sleep 20000000 | cat /etc/fstab ) &
[root@athlonz ~]# fg %1
( sleep 20000000 | cat /etc/*ease )
^Z
[1]+  Stopped                 ( sleep 20000000 | cat /etc/*ease )
[root@athlonz ~]# jobs
[1]+  Stopped                 ( sleep 20000000 | cat /etc/*ease )
[2]-  Running                 ( sleep 20000000 | cat /etc/fstab ) &
[root@athlonz ~]# bg %1
[1]+ ( sleep 20000000 | cat /etc/*ease ) &
[root@athlonz ~]# jobs
[1]-  Running                 ( sleep 20000000 | cat /etc/*ease ) &
[2]+  Running                 ( sleep 20000000 | cat /etc/fstab ) &
[root@athlonz ~]# kill %1
[root@athlonz ~]# jobs
[1]-  Terminated              ( sleep 20000000 | cat /etc/*ease )
[2]+  Running                 ( sleep 20000000 | cat /etc/fstab ) &
[root@athlonz ~]# 
[root@athlonz ~]# jobs
[2]+  Running                 ( sleep 20000000 | cat /etc/fstab ) &
[root@athlonz ~]# kill %2
[root@athlonz ~]# 
[2]+  Terminated              ( sleep 20000000 | cat /etc/fstab )
[root@athlonz ~]# 
[root@athlonz ~]# jobs
[root@athlonz ~]#

mjuckes · 11-02-2016, 03:49 AM

There seems to be an important distinction between "jobs" in the current shell and "processes" in the session. "ps" and "kill" can be used to look at and chnage the states of processes in the session (e.g. "kill -CONT $PID" to bring a suspended process back to life). "jobs" and "fg" can only be used for jobs in the current shell.