iaroki
| Name | Number | Description |
|---|---|---|
| stdin | 0 | Connected to the keyboard, most programs read input from this file |
| stdout | 1 | Attached to the screen, and all programs send their results to this file |
| stderr | 2 | Programs send status/error messages to this file which is also attached to the screen |
Redirect standard output as in the example below:
$ ls -l > ls.log
To append the output of a command, use the “>>” operator.
$ ls -l >> ls.log
Using the file descriptor number, the output redirect command above is the same as:
$ ls -l 1> ls.log
You can redirect the standard error to a file as below:
$ ls -l /root/ 2>ls-error.log
$ cat ls-error.log
It is also possible to capture all the output of a command (both standard output and standard error) into a single file. This can be done in two possible ways by specifying the file descriptor numbers:
- The first is a relatively old method which works as follows:
$ ls -l /root/ >ls-error.log 2>&1
The command above means the shell will first send the output of the ls command to the file ls-error.log (using >ls-error.log), and then writes all error messages to the file descriptor 2 (standard output) which has been redirected to the file ls-error.log (using 2>&1). Implying that standard error is also sent to the same file as standard output.
- The second and direct method is:
$ ls -l /root/ &>ls-error.log