Editing Solaris 10 Associate (section)

== Command redirection ==

* each process that korn shell creates works with file descriptors
* file descriptors determine where the input to the command originates and where the output and error messages are sent


{| border="1" cellspacing="0" cellpadding="5" align="center"
! file descriptor number
! file descriptor abbreviation
! definition
|- 
| 0
| stdin
| standard command input
|-
| 1
| stdout
| standard command output
|-
| 2
| stderr
| standard command error
|}

=== standard input ===

Less-than sign (<) forces a command to read input from file

Syntax:
* <code>command < filename</code>

<insert examples>

=== standard output ===

Greater-than sign (>) sends output from a command to a file. (>>) appends to file

Syntax:
* <code>command > filename</code>

Example of redirection:
<pre>$ echo $SHELL > file1
$ more file1
/bin/ksh
$ echo $HOME > file1
$ more file1
/export/home/paul
$ echo $SHELL >> file1
$ more file1
/export/home/paul
/bin/ksh
$</pre>

=== standard error ===

File descriptor number 2 and greater-than (>) redirects standard error to file. Redirection of standard error will suppress error messages from going to display device

Syntax:
* <code>command 2> filename</code>

<insert examples>

=== Pipe character ===

Use pipe character (|) to redirect standard output to standard input another command

Syntax:
* <code>command | command</code>

<insert examples>