the character * as the input in the unix script?

christianunix · 10-28-2007, 01:13 PM

the name of the variable that takes the user input is called "operator". What can I do to enable it to take * as the input?

Code:

 

read operator
if [ $operator = \* ]; then 

read operator
if [ $operator = "\*" ]; then 

read operator
if [ $operator = '\*' ]; then

none of the the above works!! please help me

ilikejam · 10-28-2007, 01:45 PM

Hi.

Something's not right there.
If you're doing a comparison, use '==' instead of '='.
If you're doing an assignment, use 'operator' instead of '$operator'

Dave

makyo · 10-28-2007, 04:20 PM

Hi.

Quoting will definitely help. Old-style "test" as "[" requires quoting and dereference symbol "$", whereas the new "[[" relaxes some of those restrictions. The first few parts of this show a clever scheme for doing the testing (found on this forum, but I regret that I do not recall the poster):

Code:

#!/bin/sh -

# @(#) s1       Demonstrate testing, quoting.

echo "Version used (local command version):"
version sh

# demonstrate the framework.
# "OK" means good; "KO" means bad, error, knockout.
# assignment is basically same as "read i", or "read operator".

echo
echo " i <- 1, expect OK, do not need quoting"
i=1
[ $i = 1 ] && echo OK || echo KO

echo
echo " i <- 2, expect KO, demonstrate testing framework"
i=2
[ $i = 1 ] && echo OK || echo KO

echo
echo " i <- *, special characters need quoting, expect error, KO"
i="*"
echo "i is $i"
[ $i = * ] && echo OK || echo KO

echo
echo " i <- *, quoted, if content unknown, best to quote, expect OK"
[ "$i" = "*" ] && echo OK || echo KO

echo
echo " i <- *, single quotes are more powerful, protects variable, expect KO"
[ '$i' = '*' ] && echo OK || echo KO

echo
echo " i <- *, double on variable, single on special, expect OK"
[ "$i" = '*' ] && echo OK || echo KO

echo
echo " i <- *, no dereferencing $, expect KO"
[ i = "*" ] && echo OK || echo KO

echo
echo " i <- *, double [[ allow omission of $, use of ==, expect OK"
[[ i == * ]] && echo OK || echo KO

echo
echo " simulate a read from keyboard (bash), expect OK"
read operator <<<*
echo " keyboard simulated input is \"$operator\""
[ "$operator" = "*" ] && echo OK || echo KO

exit 0

Producing:

Code:

% ./s1
Version used (local command version):
GNU bash, version 2.05b.0(1)-release (i386-pc-linux-gnu)

 i <- 1, expect OK, do not need quoting
OK

 i <- 2, expect KO, demonstrate testing framework
KO

 i <- *, special characters need quoting, expect error, KO
i is *
./s1: line 26: [: too many arguments
KO

 i <- *, quoted, if content unknown, best to quote, expect OK
OK

 i <- *, single quotes are more powerful, protects variable, expect KO
KO

 i <- *, double on variable, single on special, expect OK
OK

 i <- *, no dereferencing $, expect KO
KO

 i <- *, double [[ allow omission of $, use of ==, expect OK
OK

 simulate a read from keyboard (bash), expect OK
 keyboard simulated input is "*"
OK

Best wishes ... cheers, makyo