Ksh/Borne/Bash shell
$ ls /usr/bin
….
# when success value is 0
$ echo $?
0
$ ls /usr/bin/blah
ls: 0653-341 The file /usr/bin/blah does not exist
# when failure non-zero status
$ echo $?
1

c/Tcsh
$ ls /usr/bin
….
# when success value is 0
$ echo $status
0
$ ls /usr/bin/blah
ls: 0653-341 The file /usr/bin/blah does not exist
# when failure non-zero status
$ echo $status
1