Bash Input Redirection
If you use the shell you surely know about redirection:
# echo 'hello world' >output # cat <outputThe first line writes "hello world" to the file "output", the second reads it back and writes it to standard output (normally the terminal).
Then there are "here" documents:
# cat <<EOF > hello > world > EOFA "here" document is essentially a temporary, nameless file that is used as input to a command, here the "cat" command.
A less commonly seen form of here document is the "here" string:
# cat <<<'hello world'In this form the string following the "<<<" becomes the content of the "here" document.
Another less commonly seen form of redirection is redirecting to a specific file descriptor:
# echo 'Error: oops' >&2This redirects the output of the "echo" command to file descriptor 2, aka standard error. This is useful if you want to keep the error output of your scripts from contaminating the normal output when the output of your script is redirected.
These features work in bash and may not be available in other shells.
Mitch Frazier is an Associate Editor for Linux Journal.
|Privacy Is Personal||Jul 02, 2015|
|July 2015 Issue of Linux Journal: Mobile||Jul 01, 2015|
|July 2015 Video Preview||Jul 01, 2015|
|PHP for Non-Developers||Jun 30, 2015|
|A Code Boot Camp for Underprivileged Kids||Jun 30, 2015|
|Comprehensive Identity Management and Audit for Red Hat Enterprise Linux||Jun 29, 2015|
- Physics Analysis Workstation
- Attack of the Drones
- Django Templates
- Secure Server Deployments in Hostile Territory
- PHP for Non-Developers
- Practical Books for the Most Technical People on the Planet
- The AtoMiC Toolkit!
- Take Control of Growing Redis NoSQL Server Clusters
- Comprehensive Identity Management and Audit for Red Hat Enterprise Linux
- Privacy Is Personal