If GNU screen already exists, reattach to it, else create it

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I'm trying to do this: if a GNU screen named worker already exists, then reattach to it, else create it by starting python example.py.

I tried:

if [ls /var/run/screen/S-root/ |grep -Fxq worker] then screen -r worker else cd /home/www/example/; screen -S worker python example.py fi

but it doesn't seem to work.

Is there something wrong in the syntax?

asked Apr 18 at 19:58

Basj

6031731

What do you mean by this screen -S worker python example.py, you want to create a session and run python example.py in it ?
â€“Â Bharat
Apr 18 at 20:19

@Bharat yes, if the session is not already running and detached.
â€“Â Basj
Apr 18 at 20:20

add a commentÂ |Â

up vote
0
down vote

favorite

I'm trying to do this: if a GNU screen named worker already exists, then reattach to it, else create it by starting python example.py.

I tried:

if [ls /var/run/screen/S-root/ |grep -Fxq worker] then screen -r worker else cd /home/www/example/; screen -S worker python example.py fi

but it doesn't seem to work.

Is there something wrong in the syntax?

asked Apr 18 at 19:58

Basj

6031731

What do you mean by this screen -S worker python example.py, you want to create a session and run python example.py in it ?
â€“Â Bharat
Apr 18 at 20:19

@Bharat yes, if the session is not already running and detached.
â€“Â Basj
Apr 18 at 20:20

add a commentÂ |Â

up vote
0
down vote

favorite

I'm trying to do this: if a GNU screen named worker already exists, then reattach to it, else create it by starting python example.py.

I tried:

if [ls /var/run/screen/S-root/ |grep -Fxq worker] then screen -r worker else cd /home/www/example/; screen -S worker python example.py fi

but it doesn't seem to work.

Is there something wrong in the syntax?

asked Apr 18 at 19:58

Basj

6031731

I'm trying to do this: if a GNU screen named worker already exists, then reattach to it, else create it by starting python example.py.

I tried:

if [ls /var/run/screen/S-root/ |grep -Fxq worker] then screen -r worker else cd /home/www/example/; screen -S worker python example.py fi

but it doesn't seem to work.

Is there something wrong in the syntax?

asked Apr 18 at 19:58

Basj

6031731

asked Apr 18 at 19:58

Basj

6031731

asked Apr 18 at 19:58

Basj

6031731

asked Apr 18 at 19:58

Basj

6031731

What do you mean by this screen -S worker python example.py, you want to create a session and run python example.py in it ?
â€“Â Bharat
Apr 18 at 20:19

@Bharat yes, if the session is not already running and detached.
â€“Â Basj
Apr 18 at 20:20

add a commentÂ |Â

What do you mean by this screen -S worker python example.py, you want to create a session and run python example.py in it ?
â€“Â Bharat
Apr 18 at 20:19

@Bharat yes, if the session is not already running and detached.
â€“Â Basj
Apr 18 at 20:20

What do you mean by this screen -S worker python example.py, you want to create a session and run python example.py in it ?
â€“Â Bharat
Apr 18 at 20:19

@Bharat yes, if the session is not already running and detached.
â€“Â Basj
Apr 18 at 20:20

add a commentÂ |Â

1 Answer
1

active

oldest

votes

up vote
2
down vote

accepted

It makes more sense to use screen -ls or

screen -S worker -x || cd /home/www/example; screen -S worker python example.py;

But the errors in your code are

the unnecessary [ (which would have needed spaces around it)

if [ls /var/run/screen/S-root/ |grep -Fxq worker]

must be

if ls /var/run/screen/S-root/ | grep -Fxq worker

the missing ; / newline before then

|grep -Fxq worker] then

must be

| grep -Fxq worker; then

the missing ; / newline before else

 then screen -r worker else

must be

 then screen -r worker; else

the missing ; / newline before fi

python example.py fi

must be

python example.py; fi

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

1

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong. if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi is correct.
â€“Â Basj
Apr 18 at 20:42

add a commentÂ |Â

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1 Answer
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active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
2
down vote

accepted

It makes more sense to use screen -ls or

screen -S worker -x || cd /home/www/example; screen -S worker python example.py;

But the errors in your code are

the unnecessary [ (which would have needed spaces around it)

if [ls /var/run/screen/S-root/ |grep -Fxq worker]

must be

if ls /var/run/screen/S-root/ | grep -Fxq worker

the missing ; / newline before then

|grep -Fxq worker] then

must be

| grep -Fxq worker; then

the missing ; / newline before else

 then screen -r worker else

must be

 then screen -r worker; else

the missing ; / newline before fi

python example.py fi

must be

python example.py; fi

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

1

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong. if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi is correct.
â€“Â Basj
Apr 18 at 20:42

add a commentÂ |Â

up vote
2
down vote

accepted

It makes more sense to use screen -ls or

screen -S worker -x || cd /home/www/example; screen -S worker python example.py;

But the errors in your code are

the unnecessary [ (which would have needed spaces around it)

if [ls /var/run/screen/S-root/ |grep -Fxq worker]

must be

if ls /var/run/screen/S-root/ | grep -Fxq worker

the missing ; / newline before then

|grep -Fxq worker] then

must be

| grep -Fxq worker; then

the missing ; / newline before else

 then screen -r worker else

must be

 then screen -r worker; else

the missing ; / newline before fi

python example.py fi

must be

python example.py; fi

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

1

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong. if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi is correct.
â€“Â Basj
Apr 18 at 20:42

add a commentÂ |Â

up vote
2
down vote

accepted

It makes more sense to use screen -ls or

screen -S worker -x || cd /home/www/example; screen -S worker python example.py;

But the errors in your code are

the unnecessary [ (which would have needed spaces around it)

if [ls /var/run/screen/S-root/ |grep -Fxq worker]

must be

if ls /var/run/screen/S-root/ | grep -Fxq worker

the missing ; / newline before then

|grep -Fxq worker] then

must be

| grep -Fxq worker; then

the missing ; / newline before else

 then screen -r worker else

must be

 then screen -r worker; else

the missing ; / newline before fi

python example.py fi

must be

python example.py; fi

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

It makes more sense to use screen -ls or

screen -S worker -x || cd /home/www/example; screen -S worker python example.py;

But the errors in your code are

the unnecessary [ (which would have needed spaces around it)

if [ls /var/run/screen/S-root/ |grep -Fxq worker]

must be

if ls /var/run/screen/S-root/ | grep -Fxq worker

the missing ; / newline before then

|grep -Fxq worker] then

must be

| grep -Fxq worker; then

the missing ; / newline before else

 then screen -r worker else

must be

 then screen -r worker; else

the missing ; / newline before fi

python example.py fi

must be

python example.py; fi

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

answered Apr 18 at 20:25

Hauke Laging

53.2k1282130

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

1

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong. if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi is correct.
â€“Â Basj
Apr 18 at 20:42

add a commentÂ |Â

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

1

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong. if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi is correct.
â€“Â Basj
Apr 18 at 20:42

Thanks a lot, your solution screen -S worker -x || ... works fine. And I learnt about the missing ; + unncessary [, thanks as well!
â€“Â Basj
Apr 18 at 20:37

@Basj I use that every day because I start screen as root with the config file of my normal user account.
â€“Â Hauke Laging
Apr 18 at 20:41

Also my -Fxq was wrong.

if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi

is correct.
â€“Â Basj
Apr 18 at 20:42

Also my -Fxq was wrong.

if screen -ls |grep -Fq worker; then screen -r worker; else cd /home/www/example/; screen -S worker python example.py; fi

is correct.
â€“Â Basj
Apr 18 at 20:42

add a commentÂ |Â

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