Why does the jobs command not work in shell script?

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If I run jobs -l on command prompt it shows me the status of running jobs but if I run below file ./tmp.sh

#! /bin/bash
jobs -l

It shows empty output.

Why is that and how can I obtain information about a status of a particular job inside of a shell script?

asked May 19 '16 at 10:56

user13107

2,20982551

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up vote
2
down vote

favorite

If I run jobs -l on command prompt it shows me the status of running jobs but if I run below file ./tmp.sh

#! /bin/bash
jobs -l

It shows empty output.

Why is that and how can I obtain information about a status of a particular job inside of a shell script?

asked May 19 '16 at 10:56

user13107

2,20982551

add a commentÂ |Â

up vote
2
down vote

favorite

If I run jobs -l on command prompt it shows me the status of running jobs but if I run below file ./tmp.sh

#! /bin/bash
jobs -l

It shows empty output.

Why is that and how can I obtain information about a status of a particular job inside of a shell script?

asked May 19 '16 at 10:56

user13107

2,20982551

If I run jobs -l on command prompt it shows me the status of running jobs but if I run below file ./tmp.sh

#! /bin/bash
jobs -l

It shows empty output.

Why is that and how can I obtain information about a status of a particular job inside of a shell script?

asked May 19 '16 at 10:56

user13107

2,20982551

asked May 19 '16 at 10:56

user13107

2,20982551

asked May 19 '16 at 10:56

user13107

2,20982551

asked May 19 '16 at 10:56

user13107

2,20982551

add a commentÂ |Â

2 Answers
2

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up vote
5
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jobs

shows the jobs managed by the current shell. Your script runs inside its own shell, so jobs there will only show jobs managed by the script's shell...

To see this in action, run

#!/bin/bash
sleep 60 &
jobs -l

To see information about "jobs" started before a shell script, inside the script, you need to treat them like regular processes, and use ps etc. You can limit yourself to processes started by the parent shell (the shell from which the script was started, if any) by using the $PPID variable inside the script, and looking for processes sharing the same parent PID.

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

1

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

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up vote
0
down vote

Like Stephen said, spawning a new shell is probably not what you want to do. You have to run the code in the current shell.

Your code would work by either doing source myscript.sh or declaring your code in a function (which could be in your bashrc or a separate file that is sourced).

myfunction () 
 jobs -l

I used this in my dotfiles, if you're interested.

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
5
down vote

accepted

jobs

shows the jobs managed by the current shell. Your script runs inside its own shell, so jobs there will only show jobs managed by the script's shell...

To see this in action, run

#!/bin/bash
sleep 60 &
jobs -l

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

1

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

add a commentÂ |Â

up vote
5
down vote

accepted

jobs

shows the jobs managed by the current shell. Your script runs inside its own shell, so jobs there will only show jobs managed by the script's shell...

To see this in action, run

#!/bin/bash
sleep 60 &
jobs -l

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

1

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

add a commentÂ |Â

up vote
5
down vote

accepted

jobs

shows the jobs managed by the current shell. Your script runs inside its own shell, so jobs there will only show jobs managed by the script's shell...

To see this in action, run

#!/bin/bash
sleep 60 &
jobs -l

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

jobs

shows the jobs managed by the current shell. Your script runs inside its own shell, so jobs there will only show jobs managed by the script's shell...

To see this in action, run

#!/bin/bash
sleep 60 &
jobs -l

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

edited May 19 '16 at 11:14

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

answered May 19 '16 at 11:04

Stephen Kitt

139k22296359

1

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

add a commentÂ |Â

1

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

thanks. could you also answer how can I obtain information about a status of a particular job inside of a shell script?
â€“Â user13107
May 19 '16 at 11:06

(i'll accept your answer later in case someone has a better method) by the way, can it happen that the process id gets assigned to some other process by the system, after the original process is done? it could create a confusion then!
â€“Â user13107
May 19 '16 at 11:21

PIDs are recycled, yes. Looking at the issue more generally, to manage groups of processes together, you could use process groups or cgroups, but that feels like it's outside the scope of your question...
â€“Â Stephen Kitt
May 19 '16 at 11:37

add a commentÂ |Â

up vote
0
down vote

Like Stephen said, spawning a new shell is probably not what you want to do. You have to run the code in the current shell.

Your code would work by either doing source myscript.sh or declaring your code in a function (which could be in your bashrc or a separate file that is sourced).

myfunction () 
 jobs -l

I used this in my dotfiles, if you're interested.

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

add a commentÂ |Â

up vote
0
down vote

Like Stephen said, spawning a new shell is probably not what you want to do. You have to run the code in the current shell.

Your code would work by either doing source myscript.sh or declaring your code in a function (which could be in your bashrc or a separate file that is sourced).

myfunction () 
 jobs -l

I used this in my dotfiles, if you're interested.

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

add a commentÂ |Â

up vote
0
down vote

Like Stephen said, spawning a new shell is probably not what you want to do. You have to run the code in the current shell.

Your code would work by either doing source myscript.sh or declaring your code in a function (which could be in your bashrc or a separate file that is sourced).

myfunction () 
 jobs -l

I used this in my dotfiles, if you're interested.

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

Like Stephen said, spawning a new shell is probably not what you want to do. You have to run the code in the current shell.

Your code would work by either doing source myscript.sh or declaring your code in a function (which could be in your bashrc or a separate file that is sourced).

myfunction () 
 jobs -l

I used this in my dotfiles, if you're interested.

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

edited Feb 5 '17 at 5:05

answered Feb 5 '17 at 4:58

jasonszhao

1014

answered Feb 5 '17 at 4:58

jasonszhao

1014

answered Feb 5 '17 at 4:58

jasonszhao

1014

add a commentÂ |Â

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