The switch
statement is used to
process commands depending on the value of a variable.
When you need to handle more than three choices, switch
is a useful alternative to an if
-then
-else
statement.
If the string
variable matches pattern1
,
the first set of commands
is executed; if string
matches pattern2
, the second set of commands
is executed;
and so on. If no patterns match, execute commands
under the
default:
case.
string
can be specified using
command substitution (9.16
)
,
variable substitution (6.8
)
,
or
filename expansion (1.16
)
.
Patterns can be specified using the pattern-matching symbols *
, ?
, and
[]
. breaksw
is used to exit the switch
after commands
are executed. If breaksw
is omitted (which is rarely done),
the switch
continues to execute another set of commands
until
it reaches a breaksw
or endsw
.
Below is the general syntax of switch
, side by side with an example
that processes the first command-line argument.
switch (string
) switch ($argv[1])
case pattern1
: case -[nN]:
commands
nroff $file | lp
breaksw breaksw
case pattern2
: case -[Pp]:
commands
pr $file | lp
breaksw breaksw
case pattern3
: case -[Mm]:
commands
more $file
breaksw breaksw
. case -[Ss]:
. sort $file
. breaksw
default: default:
commands
echo "Error-no such option"
exit 1
breaksw breaksw
endsw endsw
- DG
from O'Reilly & Associates' UNIX in a Nutshell (SVR4/Solaris)