Command-Line I/O Redirection and Piping
Another way to associate a physical file with a program's logical unit number is by redirecting or piping the preconnected standard I/O files. Redirection or piping occurs on the runtime execution command.
In this way, a program that reads standard input (unit 5) and writes to standard output (unit 6) or standard error (unit 0) can, by redirection (using <, >, >>, >&, |, |&, 2>, 2>&1 on the command line), read or write to any other named file.
This is shown in the following table:
Table 2-1 csh/sh/ksh Redirection and Piping on the Command Line|
Action |
Using C Shell |
Using Bourne or Korn Shell |
|---|---|---|
|
Standard input --read from mydata | myprog < mydata | myprog < mydata |
|
Standard output --write (overwrite) myoutput | myprog > myoutput | myprog > myoutput |
|
Standard output -- write/append to myoutput | myprog >> myoutput | myprog >> myoutput |
|
Redirect standard error to a file | myprog >& errorfile | myprog 2> errorfile |
|
Pipe standard output to input of another program | myprog1 | myprog2 | myprog1 | myprog2 |
|
Pipe standard error and output to another program | myprog1 |& myprog2 | myprog1 2>&1 | myprog2 |
See the csh, ksh,and sh man pages for details on redirection and piping on the command line.
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