How to reference stdin as an option in a program in a pipeline?
I have a program that outputs a file that I want to use as stdin for the next program. However, program2 has "-in" and "-out" options that want filenames. So if I'm piping into program2, how can I reference the stdin for the "-in" option?
program1 | program2 -in stdin -out filename
bash stdin
asked Jan 7 at 19:01
MichaelMichael
1
add a comment |
I have a program that outputs a file that I want to use as stdin for the next program. However, program2 has "-in" and "-out" options that want filenames. So if I'm piping into program2, how can I reference the stdin for the "-in" option?
program1 | program2 -in stdin -out filename
bash stdin
asked Jan 7 at 19:01
MichaelMichael
1
add a comment |
I have a program that outputs a file that I want to use as stdin for the next program. However, program2 has "-in" and "-out" options that want filenames. So if I'm piping into program2, how can I reference the stdin for the "-in" option?
program1 | program2 -in stdin -out filename
bash stdin
asked Jan 7 at 19:01
MichaelMichael
1
I have a program that outputs a file that I want to use as stdin for the next program. However, program2 has "-in" and "-out" options that want filenames. So if I'm piping into program2, how can I reference the stdin for the "-in" option?
program1 | program2 -in stdin -out filename
bash stdin
bash stdin
asked Jan 7 at 19:01
MichaelMichael
1
asked Jan 7 at 19:01
MichaelMichael
1
asked Jan 7 at 19:01
MichaelMichael
1
asked Jan 7 at 19:01
MichaelMichael
1
asked Jan 7 at 19:01
MichaelMichael
1
1
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
If program2 doesn't use its stdin by itself and -in is the only way to specify the input file, these are useful options:
/proc/self/fd/0or/proc/fd/0(if available; kernel feature, not required by POSIX)
program1 | program2 -in /proc/self/fd/0 -out filename
Process substitution (supported in Bash and few other shells, not required by POSIX)
program2 -in <(program1) -out filename
Named fifo (POSIX way)
mkfifo foo
program1 >foo & # in background
program2 -in foo -out filename
rm fifo
Note that many programs that don't normally use their stdin, behave this way for a reason: they need the input file to be seekable. With <bar program2 you can make the file descriptor 0 of program2 point to the bar file which is seekable, but in general stdin is not seekable, so such programs don't bother using it. Each of the above methods may make your program fail if it expects the file to be seekable.
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
add a comment |
You can do something like
program1 > stdin & program2 -in stdin -out filename
This is not a pipe actually but will put all the stdout of program1 inside stdin file so then program2 can read it.
Alternatively some programs use the shorthand - when they attempt to read/write from shell. So it may be like:
program1 | program2 -in - -out filename
answered Jan 7 at 20:04
user1330614user1330614
1334
add a comment |
The following syntax should work in shell by pointing input file to a special file /dev/stdin:
program1 | program2 -in /dev/stdin -out filename
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
add a comment |
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3 Answers
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3 Answers
3
active
oldest
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active
oldest
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active
oldest
votes
If program2 doesn't use its stdin by itself and -in is the only way to specify the input file, these are useful options:
/proc/self/fd/0or/proc/fd/0(if available; kernel feature, not required by POSIX)
program1 | program2 -in /proc/self/fd/0 -out filename
Process substitution (supported in Bash and few other shells, not required by POSIX)
program2 -in <(program1) -out filename
Named fifo (POSIX way)
mkfifo foo
program1 >foo & # in background
program2 -in foo -out filename
rm fifo
Note that many programs that don't normally use their stdin, behave this way for a reason: they need the input file to be seekable. With <bar program2 you can make the file descriptor 0 of program2 point to the bar file which is seekable, but in general stdin is not seekable, so such programs don't bother using it. Each of the above methods may make your program fail if it expects the file to be seekable.
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
add a comment |
If program2 doesn't use its stdin by itself and -in is the only way to specify the input file, these are useful options:
/proc/self/fd/0or/proc/fd/0(if available; kernel feature, not required by POSIX)
program1 | program2 -in /proc/self/fd/0 -out filename
Process substitution (supported in Bash and few other shells, not required by POSIX)
program2 -in <(program1) -out filename
Named fifo (POSIX way)
mkfifo foo
program1 >foo & # in background
program2 -in foo -out filename
rm fifo
Note that many programs that don't normally use their stdin, behave this way for a reason: they need the input file to be seekable. With <bar program2 you can make the file descriptor 0 of program2 point to the bar file which is seekable, but in general stdin is not seekable, so such programs don't bother using it. Each of the above methods may make your program fail if it expects the file to be seekable.
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
add a comment |
If program2 doesn't use its stdin by itself and -in is the only way to specify the input file, these are useful options:
/proc/self/fd/0or/proc/fd/0(if available; kernel feature, not required by POSIX)
program1 | program2 -in /proc/self/fd/0 -out filename
Process substitution (supported in Bash and few other shells, not required by POSIX)
program2 -in <(program1) -out filename
Named fifo (POSIX way)
mkfifo foo
program1 >foo & # in background
program2 -in foo -out filename
rm fifo
Note that many programs that don't normally use their stdin, behave this way for a reason: they need the input file to be seekable. With <bar program2 you can make the file descriptor 0 of program2 point to the bar file which is seekable, but in general stdin is not seekable, so such programs don't bother using it. Each of the above methods may make your program fail if it expects the file to be seekable.
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
If program2 doesn't use its stdin by itself and -in is the only way to specify the input file, these are useful options:
/proc/self/fd/0or/proc/fd/0(if available; kernel feature, not required by POSIX)
program1 | program2 -in /proc/self/fd/0 -out filename
Process substitution (supported in Bash and few other shells, not required by POSIX)
program2 -in <(program1) -out filename
Named fifo (POSIX way)
mkfifo foo
program1 >foo & # in background
program2 -in foo -out filename
rm fifo
Note that many programs that don't normally use their stdin, behave this way for a reason: they need the input file to be seekable. With <bar program2 you can make the file descriptor 0 of program2 point to the bar file which is seekable, but in general stdin is not seekable, so such programs don't bother using it. Each of the above methods may make your program fail if it expects the file to be seekable.
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
edited Jan 7 at 20:34
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
answered Jan 7 at 20:27
Kamil MaciorowskiKamil Maciorowski
27.2k155982
27.2k155982
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
add a comment |
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
1
1
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
I'd recommend /dev/stdin instead of /proc/[self]/fd/0 -- it's not required by POSIX either, but it seems to be much more widely supported than /proc. See here and here.
– Gordon Davisson
Jan 7 at 22:42
add a comment |
You can do something like
program1 > stdin & program2 -in stdin -out filename
This is not a pipe actually but will put all the stdout of program1 inside stdin file so then program2 can read it.
Alternatively some programs use the shorthand - when they attempt to read/write from shell. So it may be like:
program1 | program2 -in - -out filename
answered Jan 7 at 20:04
user1330614user1330614
1334
add a comment |
You can do something like
program1 > stdin & program2 -in stdin -out filename
This is not a pipe actually but will put all the stdout of program1 inside stdin file so then program2 can read it.
Alternatively some programs use the shorthand - when they attempt to read/write from shell. So it may be like:
program1 | program2 -in - -out filename
answered Jan 7 at 20:04
user1330614user1330614
1334
add a comment |
You can do something like
program1 > stdin & program2 -in stdin -out filename
This is not a pipe actually but will put all the stdout of program1 inside stdin file so then program2 can read it.
Alternatively some programs use the shorthand - when they attempt to read/write from shell. So it may be like:
program1 | program2 -in - -out filename
answered Jan 7 at 20:04
user1330614user1330614
1334
You can do something like
program1 > stdin & program2 -in stdin -out filename
This is not a pipe actually but will put all the stdout of program1 inside stdin file so then program2 can read it.
Alternatively some programs use the shorthand - when they attempt to read/write from shell. So it may be like:
program1 | program2 -in - -out filename
answered Jan 7 at 20:04
user1330614user1330614
1334
answered Jan 7 at 20:04
user1330614user1330614
1334
answered Jan 7 at 20:04
user1330614user1330614
1334
answered Jan 7 at 20:04
user1330614user1330614
1334
1334
add a comment |
add a comment |
The following syntax should work in shell by pointing input file to a special file /dev/stdin:
program1 | program2 -in /dev/stdin -out filename
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
add a comment |
The following syntax should work in shell by pointing input file to a special file /dev/stdin:
program1 | program2 -in /dev/stdin -out filename
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
add a comment |
The following syntax should work in shell by pointing input file to a special file /dev/stdin:
program1 | program2 -in /dev/stdin -out filename
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
The following syntax should work in shell by pointing input file to a special file /dev/stdin:
program1 | program2 -in /dev/stdin -out filename
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
answered Jan 7 at 20:57
kenorbkenorb
11.1k1578115
11.1k1578115
add a comment |
add a comment |
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