What does 2>/dev/null mean?
I would like a brief explanation of the following command line:
grep -i 'abc' content 2>/dev/null
command-line grep redirect stdout
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
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
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
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
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
I would like a brief explanation of the following command line:
grep -i 'abc' content 2>/dev/null
command-line grep redirect stdout
command-line grep redirect stdout
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
edited Sep 6 '18 at 12:54
Zanna
50.4k13133241
50.4k13133241
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
asked Sep 26 '13 at 8:21
NaiveNaive
1,36481830
1,36481830
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
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 file1> file redirects stdout to file2> 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.
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
1
is there a difference between> /dev/null 2>&1and&> /dev/null
– Alexander Mills
Oct 19 '17 at 0:25
7
In practice today I don't think there is2>&1is 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 |
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.
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
2
Is there a good reason to use> /dev/null 2>&1instead of&> /dev/null?
– Craig McQueen
Nov 30 '15 at 6:43
6
@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/nullmay not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
– Stack Underflow
Jan 6 at 23:41
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).
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
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 file1> file redirects stdout to file2> 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.
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
1
is there a difference between> /dev/null 2>&1and&> /dev/null
– Alexander Mills
Oct 19 '17 at 0:25
7
In practice today I don't think there is2>&1is 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 file1> file redirects stdout to file2> 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.
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
1
is there a difference between> /dev/null 2>&1and&> /dev/null
– Alexander Mills
Oct 19 '17 at 0:25
7
In practice today I don't think there is2>&1is 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 file1> file redirects stdout to file2> 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.
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
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 file1> file redirects stdout to file2> 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.
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
edited Sep 26 '13 at 13:55
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
answered Sep 26 '13 at 8:38
Warren HillWarren Hill
15.4k165376
15.4k165376
1
is there a difference between> /dev/null 2>&1and&> /dev/null
– Alexander Mills
Oct 19 '17 at 0:25
7
In practice today I don't think there is2>&1is 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 |
1
is there a difference between> /dev/null 2>&1and&> /dev/null
– Alexander Mills
Oct 19 '17 at 0:25
7
In practice today I don't think there is2>&1is an older syntax so&>would not have worked years ago but both are equivalent.
– Warren Hill
Oct 19 '17 at 2:47
1
1
is there a difference between
> /dev/null 2>&1 and &> /dev/null– Alexander Mills
Oct 19 '17 at 0:25
is there a difference between
> /dev/null 2>&1 and &> /dev/null– Alexander Mills
Oct 19 '17 at 0:25
7
7
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
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 |
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.
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
2
Is there a good reason to use> /dev/null 2>&1instead of&> /dev/null?
– Craig McQueen
Nov 30 '15 at 6:43
6
@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/nullmay not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
– Stack Underflow
Jan 6 at 23:41
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.
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
2
Is there a good reason to use> /dev/null 2>&1instead of&> /dev/null?
– Craig McQueen
Nov 30 '15 at 6:43
6
@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/nullmay not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
– Stack Underflow
Jan 6 at 23:41
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.
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
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.
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
edited Sep 6 '18 at 12:57
Zanna
50.4k13133241
50.4k13133241
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
answered Sep 26 '13 at 8:32
Terry WangTerry Wang
6,31932224
6,31932224
2
Is there a good reason to use> /dev/null 2>&1instead of&> /dev/null?
– Craig McQueen
Nov 30 '15 at 6:43
6
@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/nullmay not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
– Stack Underflow
Jan 6 at 23:41
add a comment |
2
Is there a good reason to use> /dev/null 2>&1instead of&> /dev/null?
– Craig McQueen
Nov 30 '15 at 6:43
6
@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/nullmay not work in some shells but > /dev/null 2>&1 will work in all POSIX compatible shells.
– Stack Underflow
Jan 6 at 23:41
2
2
Is there a good reason to use
> /dev/null 2>&1 instead of &> /dev/null?– Craig McQueen
Nov 30 '15 at 6:43
Is there a good reason to use
> /dev/null 2>&1 instead of &> /dev/null?– Craig McQueen
Nov 30 '15 at 6:43
6
6
@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
&> 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
@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
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).
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
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).
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
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).
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
/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).
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
edited Sep 13 '18 at 6:51
Zanna
50.4k13133241
50.4k13133241
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
answered Jun 11 '15 at 10:57
Indrajeet GourIndrajeet Gour
16114
16114
add a comment |
add a comment |
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