Linux Shelling Programming Warm-up Example – $?

This shell program mainly demonstrate how to use $? to find out the exit status of command.

After a command executes, if you input to terminal: echo $?, you will get 0 or 1 to indicate the status of execution.

The following is a simple program with comments.

1. accept a string as name from command
2. use delimiter ":" to separate each line in etc/passwd file.
3. find if name you input is there
4. output a string.

echo -n "Enter a string: "
read USR
cut -d: -f1 /etc/passwd | grep "$USR" > /dev/null
#On UNIX, this is a virtual-file that can be written to. 
#Data written to this file gets discarded.
OUT=$?
if [ $OUT -eq 0 ];then
   echo "Cool! The name you input is found!"
else
   echo "The name you input doesn't exist in /etc/passwd file!"
fi
Category >> Linux  
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