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.
|Chemistry on the Desktop||Mar 23, 2017|
|Five HPC Cost Considerations to Maximize ROI||Mar 23, 2017|
|Two Ways GDPR Will Change Your Data Storage Solution||Mar 22, 2017|
|Android Candy: That App Is for the Birds!||Mar 22, 2017|
|Hodge Podge||Mar 21, 2017|
|William Rothwell and Nick Garner's Certified Ethical Hacker Complete Video Course (Pearson IT Certification)||Mar 20, 2017|
- Two Ways GDPR Will Change Your Data Storage Solution
- Hodge Podge
- Preseeding Full Disk Encryption
- Five HPC Cost Considerations to Maximize ROI
- Returning Values from Bash Functions
- Chemistry on the Desktop
- Android Candy: That App Is for the Birds!
- Two Factors Are Better Than One
- GRUB Boot from ISO