UpEnter Shell Script

Sample Output

$> ./upenter.sh 10000 ./test
parent
child
--------------------------------------------------------------------------------
child
parent
--------------------------------------------------------------------------------
Took 995 attempt(s) to get a different output

test.c

#include <stdlib.h>
#include <stdio.h>

int main() {
  int rc;

  rc = fork();
  if (rc > 0) {
    printf("parent\n");
  } else {
    printf("child\n");
  }

  return 0;
}

upenter.sh

#!/bin/sh

exiting()
{
    rm -f __1.out __2.out __err.out
    exit
}

# First argument may be integer to indicate max iterations
max=50
case $1 in
    [0-9]*) 
        max=$1
        shift
        ;;
esac


# First run
rm -f __1.out
$@ >> __1.out 2>> __err.out
# Error check
if [ ! $? -eq 0 ]; then
    cat __err.out
    exiting
fi

n=1
while [ $n -le $max ]; do
    # nth run
    rm -f __2.out
    $@ >> __2.out 2>> __err.out
    # Error check
    if [ ! $? -eq 0 ]; then
        cat __err.out
        exiting
    fi

    # Check output
    diff -q __1.out __2.out > /dev/null 2>&1
    if [ ! $? -eq 0 ]; then
        # Output differs
        cat __1.out
        echo --------------------------------------------------------------------------------
        cat __2.out
        echo --------------------------------------------------------------------------------
        echo "Took ${n} attempt(s) to get a different output"
        exiting
    fi

    # Increment and loop until $max
    n=$((${n}+1))
done

# No difference found
cat __1.out
echo --------------------------------------------------------------------------------
echo "Could not find a different output in ${max} attempt(s)"
exiting