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.
- Readers' Choice Awards 2013
- Mars Needs Women
- Linux Kernel News - November 2013
- Sublime Text: One Editor to Rule Them All?
- RSS Feeds
- Raspberry Pi: the Perfect Home Server
- December 2013 Issue of Linux Journal: Readers' Choice
- Tech Tip: Really Simple HTTP Server with Python
- IBM Will Minimize Impact of Future Disasters
- Linux Systems Administrator
- The kernel doesn't really
1 hour 58 min ago
2 hours 29 min ago
2 hours 29 min ago
4 hours 34 min ago
- This should be very helpful
5 hours 48 min ago
- As much as I share your point
8 hours 8 min ago
- So girls had it better ?
11 hours 39 min ago
- Reply to comment | Linux Journal
12 hours 4 sec ago
- why is GNOME 3 in the fifth position at 14.1 %?
17 hours 32 min ago
- Sublime Is Brilliant!
22 hours 35 min ago