Thursday, October 22, 2009

Linux : Bash Script (Shell Script)

A very simple automatic judge:

All of you studying cse must have known what is an Onlinejudge and most of us don't know how it works. Btw, I'm not going to talk about that here. It's a simple Linux Shell Scripting example / tutorial which will show you how to handle other programs in Bash and how to access all the files in a specific folder not knowing exactly how many are there.

The following snippet works very simply. It takes a target [.cpp] file as a command line argument and compiles it using g++, generates output files for all the input files provided with. And last, it compares those files with original output files and checks whether your program generated all the outputs correctly. So you can use it for your own purposes by making proper modification. It's also very easy to understand.

The folder from where you run this script must have these in it:
1. in // it will contain the input files with [.in] extension.
2. pout // it will hold the output files generated by your program.
3. jout // it will contain the correct judge output files for testing.
4. The program you are checking for with obviously [.cpp] extension and it's name is to be passed by command line argument.
Unless you change them in the code as you like. It is always a good practice to experiment with codes. :)

# Author: Zobayer Hasan
# CSE DU - 22/10/2009

# Check whether target file is provided or exists
# If available, compile and make it executableclear

if [ $# != 1 ]; then
echo "parameter missing"
elif [ ! -f "$1" ]; then
echo "file not found"
if [ -f PROG ]; then

g++ -o PROG "$1"

if [ ! -f PROG ]; then
echo "Compilation Error!"
echo "Your program could not be compiled."
echo ;

chmod -c 777 PROG > log.txt

# Run the executable for each file in the "in" directory
# And generate their output files in "pout" directory
# Then match with the correct files in "jout" directory

echo ;

values=$( ls ./in/*.in )

for LINE in $values
./PROG < "$LINE" > "./pout/$N.out"
diff ./pout/$N.out ./jout/$N.out > log.txt

if [ $? -eq 1 ]; then
echo "Wrong Answer!"
echo "For file $LINE. Check log file."
echo ;

N=$(( N + 1 ))

echo "Accepted!"
echo "All tests passed successfully."
echo ;

# End of script :)

Have fun with bash !!!


  1. Nice 1...
    Very basic but surely good to get an insight to how it works./

    1. Yes, this is a small part of my first year project. I built a software like pc^2 with the core judge running on linux.