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(, , ). , , .

, $foo, , . $- , . , .

 

1.

, :

#!/bin/sh

myvar="Hi there"

echo $myvar

echo "$myvar"

echo '$myvar'

echo \$myvar

echo Enter some text

read myvar

echo '$myvar' $myvar

exit 0

:

$./variable

Hi there

Hi there

$myvar

$myvar

Enter some text

Hello world

$myvar Hello World

myvar, Hi there. echo, , $ . , . read .

 

. , ( ), . :

$

$

$PS1 . $, bash . , [\u@\h \w]$ , , $.

$PS2 , ; >

$#

 

-

, . , $# 0.

- . 1.

1

-
$1, $2,... ,
$* , ifs.

 

. , , .

, , , .

 

test [

[ test - . [ test - , , [ ]. [ .

test , Linux, test. , , test.

test : . : test -f <_>,

if test -f fred.c then

fi

To :

if [ -f fred.c ] then

fi

test ( ) , .

[ . , , [ , test, .

then , if, test then:

if [ -f fred.c ]; then fi

, test, :

,

,

.

. 2.

2.

1 = 2 True (),
1!= 2 True (),
-n True (), null
-z True (), null ( )
1 -eq 2 True (),
1 -n 2 True (),
1 -gt 2 True (), 1 , 2
1 -g 2 True (), 1 2
1 -lt 2 True (), 1 , 2
1 -le 2 True (), 1 2
! True (), ,
-d True (),
- True (),
-f True (),
-r True (),
-s True (),
-w True (),
- True (),
     

 

2 /bin/bash.

#!/bin/sh

if [ -f /bin/bash ]

then

echo "file /bin/bash exists"

fi

 

if [ -d /bin/bash ]

then

echo "/bin/bash is a directory"

else

echo "/bin/bash is NOT a directory"

fi

, , . test, .

 

, .

, , .

 

if

if : .

if then

else

fi

if , , .

3

#!/bin/sh

echo " ? yes no"

read timeofday

if [ $timeofday = "yes" ]; then

echo " "

else

echo " "

fi

exit 0

:

? yes no yes

yes

$

timeofday [. if, .

, if ; .

 

elif

, . -, n () yes (). , elif, , else if ( 4).

, , - yes n. else elif :

4

#!/bin/sh

echo " ? yes no"

read timeofday

if [ $timeofday = "yes" ]

then

echo " "

elif [ $timeofday = "no" ]; then

echo " "

else

echo ", $timeofday . yes no "

exit 1

fi

exit 0

 

4 , , true, elif . , , 1, .

,

, . , <Enter>. :

[: =: unary operator expected

? if. timeofday, . , if : if [ = "yes" ] . : if [ "$timeofday" = "yes" ]

:

if [ "" = "yes" ]

:

5.

#!/bin/sh

echo " ? yes no "

read timeofday

if [ "$timeofday " = "yes" ]

then

echo " "

elif [ "$timeofday" = "no" ]; then

echo " "

else

echo ", $timeofday . yes no "

exit 1

fi

exit 0

 

, <Enter>.

. , echo , printf (. "printf" ) echo. bash echo n. :

echo -n " ? yes no: "

.

 





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