, UNIX, . , 1. , , $1, - $2, .. $0 - ' , ( , ) - . . , ' (. ).
6.1.14
bash let, . , . let . let, , . , . :
$ let "res = 2 * 7"
$ echo $res
$
6.1.15 test
, . test , , . - test, , , $?. test . :
$ greeting="hallo"
$ num=5
$ test $num -eq 5; echo $?
$ [ $greeting = "hallo" ]; echo $?
$ test -f main.c; echo $?
. ( , =, - -eq). - main.c . ( ). test .
bash , . , .
if . ֳ . ( ), if . else ( ) if- . if fi (if ). if- :
if <->
then
<>
else
<>
fi
- test - [].
|
|
|
if elif. elif . elif else:
if <->
then
<>
elif
<>
else
<>
fi
case . . , () ' . , . , , . esac (case ). :
case <> in
)
;;
)
;;
*)
;;
esac
: *, [],?, |. '.
. while , ( - ). done:
while <->
do
done
if-, - test ( ).
until while. ³ , , :
until <->
do
done
for-in , . - . . , . ҳ do-done, for-in:
for <> in <_>
do
done
for . , - , .
6.1.18
whoareyou. :
echo What is your name? (1)
read reply (2)
case $reply in (3)
root) (4)
echo You are system administrator of $HOSTNAME (5)
;; (6)
stud) (7)
echo You are a student (8)
;; (9)
*) (10)
echo You are a mortal user on $HOSTNAME (11)
;; (12)
esac (13)
( 1). ', reply. reply ( , ). . - HOSTNAME. ' UNIX-, .
. , , . chkown , .
for filename in `ls` (1)
do (2)
if [! -O $filename ]; then (3)
|
|
|
echo $filename does not belong to `whoami` (4)
fi (5)
if [ -d $filename -a -x $filename ]; then (6)
echo Entering $filename... (7)
cd $filename (8)
$0 (9)
Echo Leaving $filename... (10)
cd.. (11)
fi (12)
done (13)
.
for-. filename. ls ( ). , filename .
3 , , ( -O test). , then , , (;). ( - ), ( 4). 4 `whoami` echo ' ( ).
6 : filename ( -d), filename , (-x). ( -a "") , , then . , (cd).
filename ' , ( 8) ( 9 $0 , ). ϳ , , ( 11), then .
, PATH, , ( ), chkown. 9 , PATH .
