special variable in Linux that stores the last command output?

rockstar05 · 06-23-2015, 02:05 AM

Is there a special variable in Linux that stores the last command output?

Kindly let me know if there is any?

rhubarbdog · 06-23-2015, 02:59 AM

which output to be clear. stdout, stderr or the exit code

rhubarbdog · 06-23-2015, 03:00 AM

also what shell script language are you using
bash dash sh another?

astrogeek · 06-23-2015, 03:04 AM

If using bash, and if you mean the exit status of the last command, it is $?.

See more info here.

rockstar05 · 06-23-2015, 03:18 AM

Not the Exit status, I want to know if there is any variable that stores the output of previous Linux command.

I am using bash scripting Language.

Thanks.

astrogeek · 06-23-2015, 03:23 AM

Keith Hedger · 06-23-2015, 03:36 AM

No but you can use '>' to redirect to a file or use the 'tee' command to redirect to a file and to stdout, you can also use command substitution like so

Code:

keithhedger@LFSCerebro:~-> x=$(ls)
keithhedger@LFSCerebro:~-> echo $x
backdrops bashrc cdtdebugger conky ConkyThemes Desktop Desktop-1 Desktop.BAK Desktop.bak2 Documents Downloads Dropbox Dropbox.ini Dump examples googledirectlink kkedit-0.2.2-1.1.x86_64.cpio kkeditdebug lddgrep LFSPkgBuildScripts lfssession.pid Maildir Necronomicon.swf noip-duc-linux noip-duc-linux.tar.gz osx.vnc Patterns Projects PythonScripts quarantine Scripts SpaceFMScripts startnewx SVN temails Templates testhomenet.grsync VBox VBShared Wallpapers workspace-cdtdebug xfce4-meta.LFSBuild.BAK xinits

Sefyir · 06-23-2015, 08:29 AM

To check for yourself, type this in the terminal and hit Alt+Shift+*

Code:

echo $

It (should) auto-complete onto the terminal all of your variables in your environment. Then by hitting enter you can see what each variable holds (empty ones will show nothing)

Keith Hedger · 06-23-2015, 08:36 AM

TAB is the standard auto complete key, if you want to see all variable use 'env'

Sefyir · 06-23-2015, 08:39 AM

TAB lists all options and will let you autocomplete one into the terminal (with usage of * to sometimes act upon multiple options).
Alt-* causes bash to take all of those available options and put them into the command line - which can then be acted upon.
Different keys for different purposes.

However, I was not aware of env - thank you.

Code:

       insert-completions (M-*)
              Insert all completions of the text before point that would have been generated by possible-com
              pletions.
       complete (TAB)
              Attempt to perform completion on the text before point.  Bash attempts completion treating  the
              text  as a variable (if the text begins with $), username (if the text begins with ~), hostname
              (if the text begins with @), or command (including aliases and functions) in turn.  If none  of
              these produces a match, filename completion is attempted.

linom · 06-23-2015, 09:11 AM

In bash, you can try:
~# echo $_
But, there also has some limitation. A command with parameters / arguments, shall return the last part.
For eg. if the last command is
~# ls -l
the command ~# echo $_ will return only the second part, i.e. "-l"