Shell scripting: Few parameter expansion related questions
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Give brief answers for the following questions.
1. Can an until loop sometimes never execute?
2. Will the following script execute with no errors?
#!/bin/csh
for I
do
echo $I
done
3. Does the following script print to standard output, a list of numbers equal to the number passed on the command line?
#!/bin/sh
count=$1
index=1
while [ "0$index" -le $count ]
do
echo $index
index=`expr "$index" + 1`
done
4. Will the following statement print 'I am glad this class is over' to standard output if the shell variable XYZ is NULL or not set?
: ${XYZ:?"I am glad this class is over"}
5. After the statement
: ${VISUAL:=vi}
will the value of the shell variable VISUAL always be vi?
6. Will the following command execute:
${VISUAL:+vi} ls
the command 'ls' if the shell variable VISUAL is not set or null?
7. Will the following commands send to the line printer all files whose contents contain the text '/bin/sh' if the command to print is lpr ?
MATCH=`grep -l '/bin/sh' *`
lpr ${MATCH?"NO files found"}
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Solution Summary
Solution also gives reasons/examples in many cases.
Solution Preview
1. Yes, sometimes an until loop will never execute. Consider the example given below.
#!/bin/bash
myvar=5
until [ $myvar ...
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