pages:howtos:bash:bash-io-redirection
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| pages:howtos:bash:bash-io-redirection [2021/02/11 19:05] – created mischerh | pages:howtos:bash:bash-io-redirection [2021/12/09 22:00] (current) – [I/O Redirection] rokkitlawnchair | ||
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| Line 4: | Line 4: | ||
| For example, if we have a program called do_something that reads from stdin and writes to stdout and stderr, we can change its input source by using the less-than sign ( < ) followed by the name of the file to be consumed for input data: | For example, if we have a program called do_something that reads from stdin and writes to stdout and stderr, we can change its input source by using the less-than sign ( < ) followed by the name of the file to be consumed for input data: | ||
| + | <sxh bash; gutter: false> | ||
| do_something < input-file | do_something < input-file | ||
| + | </ | ||
| If you want to send the output to a file, use the greater-than sign ( > ) as in: | If you want to send the output to a file, use the greater-than sign ( > ) as in: | ||
| + | <sxh bash; gutter: false> | ||
| do_something > output-file | do_something > output-file | ||
| + | </ | ||
| Because stderr is not the same as stdout, error messages will still be seen on the terminal windows in the above example. | Because stderr is not the same as stdout, error messages will still be seen on the terminal windows in the above example. | ||
| If you want to redirect stderr to a separate file, you use stderr’s file descriptor number (2), the greater-than sign ( > ), followed by the name of the file you want to hold everything the running command writes to stderr: | If you want to redirect stderr to a separate file, you use stderr’s file descriptor number (2), the greater-than sign ( > ), followed by the name of the file you want to hold everything the running command writes to stderr: | ||
| - | + | <sxh bash; gutter: false> | |
| - | $ do_something 2> error-file | + | do_something 2> error-file |
| + | </ | ||
| A special shorthand notation can be used to put anything written to file descriptor 2 (stderr) in the same place as file descriptor 1 (stdout): 2>&1 | A special shorthand notation can be used to put anything written to file descriptor 2 (stderr) in the same place as file descriptor 1 (stdout): 2>&1 | ||
| + | <sxh bash; gutter: false> | ||
| do_something > all-output-file 2>&1 | do_something > all-output-file 2>&1 | ||
| + | </ | ||
| bash permits an easier syntax for the above: | bash permits an easier syntax for the above: | ||
| + | <sxh bash; gutter: false> | ||
| do_something >& all-output-file | do_something >& all-output-file | ||
| + | </ | ||
| + | ---- | ||
| + | ~~DISCUSSION~~ | ||
pages/howtos/bash/bash-io-redirection.1613070318.txt.gz · Last modified: 2021/02/11 19:05 by mischerh