Run another command when previous command completes [duplicate]

This question already has an answer here:

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

6 answers

Today I opened gnome-terminal and I wrote

ls && sleep 4 && gnome-terminal

to open another terminal after the completion of ls command and waiting for 4 seconds.
So it successfully opened a new terminal after previous commands completely ran (including sleep 4).

After that, next time I typed a new command

ls -lR && sleep 4 && gnome-terminal

The command ls -lR completed after 3 seconds, but after that none of the commands sleep 4 and gnome-terminal ran successfully.

What is the problem?

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

marked as duplicate by karel, Charles Green, Dan, dessert command-line
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Jan 29 at 18:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a comment |

This question already has an answer here:

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

6 answers

Today I opened gnome-terminal and I wrote

ls && sleep 4 && gnome-terminal

to open another terminal after the completion of ls command and waiting for 4 seconds.
So it successfully opened a new terminal after previous commands completely ran (including sleep 4).

After that, next time I typed a new command

ls -lR && sleep 4 && gnome-terminal

The command ls -lR completed after 3 seconds, but after that none of the commands sleep 4 and gnome-terminal ran successfully.

What is the problem?

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

marked as duplicate by karel, Charles Green, Dan, dessert command-line
Users with the command-line badge can single-handedly close command-line questions as duplicates and reopen them as needed.

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Jan 29 at 18:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a comment |

This question already has an answer here:

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

6 answers

Today I opened gnome-terminal and I wrote

ls && sleep 4 && gnome-terminal

to open another terminal after the completion of ls command and waiting for 4 seconds.
So it successfully opened a new terminal after previous commands completely ran (including sleep 4).

After that, next time I typed a new command

ls -lR && sleep 4 && gnome-terminal

The command ls -lR completed after 3 seconds, but after that none of the commands sleep 4 and gnome-terminal ran successfully.

What is the problem?

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

This question already has an answer here:

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

6 answers

Today I opened gnome-terminal and I wrote

ls && sleep 4 && gnome-terminal

to open another terminal after the completion of ls command and waiting for 4 seconds.
So it successfully opened a new terminal after previous commands completely ran (including sleep 4).

After that, next time I typed a new command

ls -lR && sleep 4 && gnome-terminal

The command ls -lR completed after 3 seconds, but after that none of the commands sleep 4 and gnome-terminal ran successfully.

What is the problem?

This question already has an answer here:

Is there a difference between the '&&' and ';' symbols in a standard BASH terminal?

6 answers

command-line bash syntax

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

edited Jan 28 at 19:46

wjandrea

9,45842664

edited Jan 28 at 19:46

wjandrea

9,45842664

edited Jan 28 at 19:46

wjandrea

9,45842664

asked Jan 28 at 16:34

Abhishek Kamal

15011

asked Jan 28 at 16:34

Abhishek Kamal

15011

asked Jan 28 at 16:34

Abhishek Kamal

15011

marked as duplicate by karel, Charles Green, Dan, dessert command-line
Users with the command-line badge can single-handedly close command-line questions as duplicates and reopen them as needed.

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Jan 29 at 18:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

marked as duplicate by karel, Charles Green, Dan, dessert command-line
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Jan 29 at 18:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

add a comment |

2 Answers
2

active

oldest

votes

&& means to run it if the previous command was successful. In Unix that generally means exit status 0.

$ ls barfoofba && echo "This will not be echo'd"

ls: cannot access 'barfoofba': No such file or directory

$ ls bar && echo "This will be echo'd"  

This will be echo'd

In the first instance, ls did not succeed, so it exited with a non-zero exit status, and bash did not run the second command.

In the second example, I ls'd a existing file, so ls exited with 0 as exit status, and the command was executed.

If you want to run commands unconditionally, e.g. not dependent on the result of the first, you may separate them with ; like this

 command1; command2; command3

and so forth.

Thus you may do

ls -lR ; sleep 4 ; gnome-terminal

In addition to && and ; you have || which is the opposite of &&: Only run the command if the previous command failed with a non-zero exit status. If the first command succeeds, the next will not be executed. If it fails, the next will be executed.

So in short:

&&: Run if preceding command exited with 0

;: Run unconditionally

||: Run if preceding command exited with a non-zero exit status.

&: Run both commands in paralell, the first in background and second in foreground.

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

6

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

4

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

3

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

2

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

2

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

|
show 4 more comments

The command ls -lR exited with an exit-status different than zero, so the following commands have not been executed. Most probably ls was unable to open a subdirectory. It didn't happen in your first command because you didn't use the -R-option.

From man bash:

        command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status

       of zero.

From man ls:

Exit status:

       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory)

       2      if serious trouble (e.g., cannot access command-line argument).

answered Jan 28 at 16:51

mook765

4,37321333

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

add a comment |

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

&& means to run it if the previous command was successful. In Unix that generally means exit status 0.

$ ls barfoofba && echo "This will not be echo'd"

ls: cannot access 'barfoofba': No such file or directory

$ ls bar && echo "This will be echo'd"  

This will be echo'd

In the first instance, ls did not succeed, so it exited with a non-zero exit status, and bash did not run the second command.

In the second example, I ls'd a existing file, so ls exited with 0 as exit status, and the command was executed.

If you want to run commands unconditionally, e.g. not dependent on the result of the first, you may separate them with ; like this

 command1; command2; command3

and so forth.

Thus you may do

ls -lR ; sleep 4 ; gnome-terminal

So in short:

&&: Run if preceding command exited with 0

;: Run unconditionally

||: Run if preceding command exited with a non-zero exit status.

&: Run both commands in paralell, the first in background and second in foreground.

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

6

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

4

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

3

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

2

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

2

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

|
show 4 more comments

&& means to run it if the previous command was successful. In Unix that generally means exit status 0.

$ ls barfoofba && echo "This will not be echo'd"

ls: cannot access 'barfoofba': No such file or directory

$ ls bar && echo "This will be echo'd"  

This will be echo'd

In the first instance, ls did not succeed, so it exited with a non-zero exit status, and bash did not run the second command.

In the second example, I ls'd a existing file, so ls exited with 0 as exit status, and the command was executed.

If you want to run commands unconditionally, e.g. not dependent on the result of the first, you may separate them with ; like this

 command1; command2; command3

and so forth.

Thus you may do

ls -lR ; sleep 4 ; gnome-terminal

So in short:

&&: Run if preceding command exited with 0

;: Run unconditionally

||: Run if preceding command exited with a non-zero exit status.

&: Run both commands in paralell, the first in background and second in foreground.

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

6

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

4

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

3

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

2

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

2

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

|
show 4 more comments

&& means to run it if the previous command was successful. In Unix that generally means exit status 0.

$ ls barfoofba && echo "This will not be echo'd"

ls: cannot access 'barfoofba': No such file or directory

$ ls bar && echo "This will be echo'd"  

This will be echo'd

In the first instance, ls did not succeed, so it exited with a non-zero exit status, and bash did not run the second command.

In the second example, I ls'd a existing file, so ls exited with 0 as exit status, and the command was executed.

If you want to run commands unconditionally, e.g. not dependent on the result of the first, you may separate them with ; like this

 command1; command2; command3

and so forth.

Thus you may do

ls -lR ; sleep 4 ; gnome-terminal

So in short:

&&: Run if preceding command exited with 0

;: Run unconditionally

||: Run if preceding command exited with a non-zero exit status.

&: Run both commands in paralell, the first in background and second in foreground.

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

&& means to run it if the previous command was successful. In Unix that generally means exit status 0.

$ ls barfoofba && echo "This will not be echo'd"

ls: cannot access 'barfoofba': No such file or directory

$ ls bar && echo "This will be echo'd"  

This will be echo'd

In the first instance, ls did not succeed, so it exited with a non-zero exit status, and bash did not run the second command.

In the second example, I ls'd a existing file, so ls exited with 0 as exit status, and the command was executed.

If you want to run commands unconditionally, e.g. not dependent on the result of the first, you may separate them with ; like this

 command1; command2; command3

and so forth.

Thus you may do

ls -lR ; sleep 4 ; gnome-terminal

So in short:

&&: Run if preceding command exited with 0

;: Run unconditionally

||: Run if preceding command exited with a non-zero exit status.

&: Run both commands in paralell, the first in background and second in foreground.

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

edited Jan 29 at 16:58

answered Jan 28 at 16:46

vidarlo

10.5k52751

answered Jan 28 at 16:46

vidarlo

10.5k52751

answered Jan 28 at 16:46

vidarlo

10.5k52751

6

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

4

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

3

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

2

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

2

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

|
show 4 more comments

6

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

4

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

3

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

2

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

2

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

I think of it like 0 means SUCCESS which is like true.

– Jason Goemaat
Jan 29 at 0:00

@KodosJohnson In the C world, 0 means success because non-zero means an error, and there could be hundreds of error codes (see error.h). Happy return codes are all alike...

– chrylis
Jan 29 at 2:48

@AbhishekKamal No, I can't try on my machine. ls -lR should work, but it might fail if it for instance hits one directory it doesn't have permissions to look in. For instance will ls -lR / always fail...

– vidarlo
Jan 29 at 5:53

@JonBentley The "echo" in "echo'd" is the name of a command, not an English verb, even if it happens to be spelled the same, so it's somewhat open to question how it should be conjugated. This is more obvious if you pick other commands: what would the past tense of ls be, for instance?

– IMSoP
Jan 29 at 15:29

@chrylis: No, the point is exactly that "0 for true" is not how it is "in the C world". In the C programming language, conditionals (and the logical operators) consider 0 to be false and everything else to be true. The convention for process exit codes in the shell is exactly the opposite. -- Even though both C and the shell are both parts of a larger Unix tradition.

– Henning Makholm
Jan 29 at 16:55

|
show 4 more comments

From man bash:

        command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status

       of zero.

From man ls:

Exit status:

       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory)

       2      if serious trouble (e.g., cannot access command-line argument).

answered Jan 28 at 16:51

mook765

4,37321333

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

add a comment |

From man bash:

        command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status

       of zero.

From man ls:

Exit status:

       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory)

       2      if serious trouble (e.g., cannot access command-line argument).

answered Jan 28 at 16:51

mook765

4,37321333

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

add a comment |

From man bash:

        command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status

       of zero.

From man ls:

Exit status:

       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory)

       2      if serious trouble (e.g., cannot access command-line argument).

answered Jan 28 at 16:51

mook765

4,37321333

From man bash:

        command1 && command2

       command2  is  executed if, and only if, command1 returns an exit status

       of zero.

From man ls:

Exit status:

       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory)

       2      if serious trouble (e.g., cannot access command-line argument).

answered Jan 28 at 16:51

mook765

4,37321333

answered Jan 28 at 16:51

mook765

4,37321333

answered Jan 28 at 16:51

mook765

4,37321333

answered Jan 28 at 16:51

mook765

4,37321333

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

add a comment |

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

Thanks @mook765, Your answer is perfect according to my question.. I cleared my confusion

– Abhishek Kamal
Jan 29 at 1:50

According to your answer, when i run ls -lR && sleep 4 && gnome-terminal with sudo, it successfully runs.

– Abhishek Kamal
Jan 29 at 1:52

add a comment |

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