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What does 2>/dev/null mean?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

196

100

I would like a brief explanation of the following command line:

grep -i 'abc' content 2>/dev/null 

command-line grep redirect stdout

share|improve this question

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

add a comment | 

196

100

I would like a brief explanation of the following command line:

grep -i 'abc' content 2>/dev/null 

command-line grep redirect stdout

share|improve this question

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

add a comment | 

I would like a brief explanation of the following command line:

grep -i 'abc' content 2>/dev/null 

command-line grep redirect stdout

share|improve this question

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

grep -i 'abc' content 2>/dev/null 

share|improve this question

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

share|improve this question

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

edited Sep 6 '18 at 12:54

Zanna

51.4k13140243

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

asked Sep 26 '13 at 8:21

NaiveNaive

1,48991830

3 Answers
3

active

oldest

votes

286

The > operator redirects the output usually to a file but it can be to a device. You can also use >> to append.

If you don't specify a number then the standard output stream is assumed but you can also redirect errors

> file redirects stdout to file
1> file redirects stdout to file
2> file redirects stderr to file
&> file redirects stdout and stderr to file

/dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output.

share|improve this answer

edited Sep 26 '13 at 13:55

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  is there a difference between > /dev/null 2>&1 and &> /dev/null
  
  – Alexander Mills
  Oct 19 '17 at 0:25
  

  
  
  
  


• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  In practice today I don't think there is 2>&1 is an older syntax so &> would not have worked years ago but both are equivalent.
  
  – Warren Hill
  Oct 19 '17 at 2:47
  

  
  
  
  

add a comment | 

19

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command).

Some more common use cases for redirection:

command > /dev/null 2>&1 &

Run command in the background, discard stdout and stderr

command >> /path/to/log 2>&1 &

Run command and append stdout and stderr to a log file.

share|improve this answer

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Is there a good reason to use > /dev/null 2>&1 instead of &> /dev/null?
  
  – Craig McQueen
  Nov 30 '15 at 6:43
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  
  @CraigMcQueen &> is new in Bash 4, the former is just the traditional way, I am just so used to it (easy to remember).
  
  – Terry Wang
  Nov 30 '15 at 12:24
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @CraigMcQueen according to a comment on this answer, &> /dev/null may not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
  
  – Stack Underflow
  Jan 6 at 23:41
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Why is it 2>&1 and not 2&1> ??
  
  – marienbad
  Mar 11 at 21:30
  

  
  
  
  

add a comment | 

8

/dev/null is treated as black hole in Linux/Unix, so you can put anything into this but you will not be able to get it back from /dev/null.

Further, 2> means that you are redirecting (i.e. >) the stderr (i.e. 2) into the black hole (i.e. /dev/null)

Your command is:

grep -i 'abc' content 2>/dev/null 

Don't try to end with another forward slash like this - 2>/dev/null/ (it's not a directory).

share|improve this answer

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

add a comment | 

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286

The > operator redirects the output usually to a file but it can be to a device. You can also use >> to append.

If you don't specify a number then the standard output stream is assumed but you can also redirect errors

> file redirects stdout to file
1> file redirects stdout to file
2> file redirects stderr to file
&> file redirects stdout and stderr to file

/dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output.

share|improve this answer

edited Sep 26 '13 at 13:55

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  is there a difference between > /dev/null 2>&1 and &> /dev/null
  
  – Alexander Mills
  Oct 19 '17 at 0:25
  

  
  
  
  


• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  In practice today I don't think there is 2>&1 is an older syntax so &> would not have worked years ago but both are equivalent.
  
  – Warren Hill
  Oct 19 '17 at 2:47
  

  
  
  
  

add a comment | 

286

The > operator redirects the output usually to a file but it can be to a device. You can also use >> to append.

If you don't specify a number then the standard output stream is assumed but you can also redirect errors

> file redirects stdout to file
1> file redirects stdout to file
2> file redirects stderr to file
&> file redirects stdout and stderr to file

/dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output.

share|improve this answer

edited Sep 26 '13 at 13:55

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  is there a difference between > /dev/null 2>&1 and &> /dev/null
  
  – Alexander Mills
  Oct 19 '17 at 0:25
  

  
  
  
  


• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  In practice today I don't think there is 2>&1 is an older syntax so &> would not have worked years ago but both are equivalent.
  
  – Warren Hill
  Oct 19 '17 at 2:47
  

  
  
  
  

add a comment | 

The > operator redirects the output usually to a file but it can be to a device. You can also use >> to append.

If you don't specify a number then the standard output stream is assumed but you can also redirect errors

> file redirects stdout to file
1> file redirects stdout to file
2> file redirects stderr to file
&> file redirects stdout and stderr to file

/dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output.

share|improve this answer

edited Sep 26 '13 at 13:55

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

share|improve this answer

edited Sep 26 '13 at 13:55

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

answered Sep 26 '13 at 8:38

Warren HillWarren Hill

16.1k165477

19

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command).

Some more common use cases for redirection:

command > /dev/null 2>&1 &

Run command in the background, discard stdout and stderr

command >> /path/to/log 2>&1 &

Run command and append stdout and stderr to a log file.

share|improve this answer

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Is there a good reason to use > /dev/null 2>&1 instead of &> /dev/null?
  
  – Craig McQueen
  Nov 30 '15 at 6:43
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  
  @CraigMcQueen &> is new in Bash 4, the former is just the traditional way, I am just so used to it (easy to remember).
  
  – Terry Wang
  Nov 30 '15 at 12:24
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @CraigMcQueen according to a comment on this answer, &> /dev/null may not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
  
  – Stack Underflow
  Jan 6 at 23:41
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Why is it 2>&1 and not 2&1> ??
  
  – marienbad
  Mar 11 at 21:30
  

  
  
  
  

add a comment | 

19

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command).

Some more common use cases for redirection:

command > /dev/null 2>&1 &

Run command in the background, discard stdout and stderr

command >> /path/to/log 2>&1 &

Run command and append stdout and stderr to a log file.

share|improve this answer

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Is there a good reason to use > /dev/null 2>&1 instead of &> /dev/null?
  
  – Craig McQueen
  Nov 30 '15 at 6:43
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  
  @CraigMcQueen &> is new in Bash 4, the former is just the traditional way, I am just so used to it (easy to remember).
  
  – Terry Wang
  Nov 30 '15 at 12:24
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @CraigMcQueen according to a comment on this answer, &> /dev/null may not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
  
  – Stack Underflow
  Jan 6 at 23:41
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Why is it 2>&1 and not 2&1> ??
  
  – marienbad
  Mar 11 at 21:30
  

  
  
  
  

add a comment | 

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command).

Some more common use cases for redirection:

command > /dev/null 2>&1 &

Run command in the background, discard stdout and stderr

command >> /path/to/log 2>&1 &

Run command and append stdout and stderr to a log file.

share|improve this answer

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

command > /dev/null 2>&1 &

command >> /path/to/log 2>&1 &

share|improve this answer

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

edited Sep 6 '18 at 12:57

Zanna

51.4k13140243

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

answered Sep 26 '13 at 8:32

Terry WangTerry Wang

6,53932224

8

/dev/null is treated as black hole in Linux/Unix, so you can put anything into this but you will not be able to get it back from /dev/null.

Further, 2> means that you are redirecting (i.e. >) the stderr (i.e. 2) into the black hole (i.e. /dev/null)

Your command is:

grep -i 'abc' content 2>/dev/null 

Don't try to end with another forward slash like this - 2>/dev/null/ (it's not a directory).

share|improve this answer

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

add a comment | 

8

/dev/null is treated as black hole in Linux/Unix, so you can put anything into this but you will not be able to get it back from /dev/null.

Further, 2> means that you are redirecting (i.e. >) the stderr (i.e. 2) into the black hole (i.e. /dev/null)

Your command is:

grep -i 'abc' content 2>/dev/null 

Don't try to end with another forward slash like this - 2>/dev/null/ (it's not a directory).

share|improve this answer

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

add a comment | 

/dev/null is treated as black hole in Linux/Unix, so you can put anything into this but you will not be able to get it back from /dev/null.

Further, 2> means that you are redirecting (i.e. >) the stderr (i.e. 2) into the black hole (i.e. /dev/null)

Your command is:

grep -i 'abc' content 2>/dev/null 

Don't try to end with another forward slash like this - 2>/dev/null/ (it's not a directory).

share|improve this answer

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

grep -i 'abc' content 2>/dev/null 

share|improve this answer

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

edited Sep 13 '18 at 6:51

Zanna

51.4k13140243

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114

answered Jun 11 '15 at 10:57

Indrajeet GourIndrajeet Gour

18114