echo command

vinothaa · 06-04-2010, 09:21 PM

this is vinoth. what is the use of echo $? in redhat linux.pls explain it.

regards
vinoth

AlucardZero · 06-04-2010, 09:26 PM

it returns the exit status of the most recent command run.

you should look up some beginner's books for Linux and shell scripting and read them.

John VV · 06-04-2010, 09:28 PM

this sounds like homework
look at " man echo " or search google/linux http://www.google.com/linux

jim.yefeng · 06-04-2010, 10:47 PM

Shell uses negative logic.
In general, $? equals 0 denotes the execution of previous command is successful.

timmeke · 06-05-2010, 07:24 AM

Quote:

Originally Posted by jim.yefeng

Shell uses negative logic.
In general, $? equals 0 denotes the execution of previous command is successful.

The meaning of the exit code 0 can vary depending on the application. By convention, 0 means successful run. This is a convention of app developers more than it is "built in" logic of the shell.

druuna · 06-05-2010, 08:15 AM

Hi,

In addition to timmeke's reply: Not 0 doesn't necessarily mean the program ran unsuccessful.

Example: Grep can return 1, that tells you grep did not find the pattern given. Which could be what you wanted....

Always look at the manual page/documentation to find out where these numbers stand for.