View source for SPR720 BASH Scripting Lab

= Running a Bash Script =

Enter this script into the file "script1" in the current directory (it's a good idea to create a directory for this lab):

 #!/bin/bash
 SECRET=$(( RANDOM % 100 + 1))
 INPUT=0
 GUESSES=0
 
 echo "Guess the secret: a number between 1 and 100."
 while [ "$INPUT" -ne "$SECRET" ]
 do
 
        echo -n "Your guess: "
        read INPUT
 
        if [ "$INPUT" -eq "$SECRET" ]
        then
                echo "Correct!"
        elif [ "$INPUT" -gt "$SECRET" ]
        then
                echo "Too high."
        else
                echo "Too low."
        fi
 
        ((GUESSES++))
 
 done
 
 echo "You took $GUESSES tries."

Make the script executable:

 chmod u+x script1

Try running the script:

 script1

If that doesn't work, specify the directory:

 ./script1

Or add the current directory to the path:

 PATH="$PATH:."

Read through the script and make sure you understand what it does. Use [[BASH]] wiki page and the bash manpage for reference.

= Reading Bash Scripts =

Guess what each of these scripts does, and then test your assumption.

 #!/bin/bash
  
 if false
 then
         echo "1"
 elif true
 then
         echo "2"
 else
         echo "3"
 fi

 #!/bin/bash
 for ((x=0; x<5; x++))
 do
    echo $x
 done

 #!/bin/bash
 for NAME in /etc/*
 do
   if [ -r "$NAME" -a -f "$NAME" ]
   then
      wc -c "$NAME"
   fi
 done

= Writing [[BASH]] Scripts =

Write scripts to do three of the following tasks:

# Loop through the files in your home directory, and for each readable file, ask whether the file should be printed, mailed to you, or ignored (P/M/I) and then take the appropriate action.
# Display the longest and shortest usernames on the system (usernames are in the first field in /etc/passwd).
# Count the number of users with user IDs between 500 and 10000 on the system (user IDs are the third field in /etc/passwd).
# Display the names of any filesystems which have less than 10% free space available (see the <code>df</code> command for this information).
# Ask the user for an e-mail address, then send the output of the <code>dmesg</code> command to that address.
# Count the number of files in the user's home directory which are not readable.
# For each directory in the $PATH, display the number of executable files in that directory.

== Hints and suggestions ==

See the manpages for these commands:

* wc (see the -w, -c, -l, and -L options)
* lpr
* mail
* cut (see the -d and -f options)
* df

= Deliverable =

Blog about your experience with this lab, and include a link to one of the scripts you've written.

[[Category:SPR720]]