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Shell script implementation of a Queue.
#!/bin/bash
#
# This script encapsulates the functionality of a queue. It requires there to be
# an input file with the data in the queue being separated on different lines.
#
INPUT=queue.txt
OUTPUT=trash.txt
CMD=/usr/bin/vlc
if [ ! -f "$INPUT" ] ; then
touch "$INPUT"
fi
#
# poll() removes the top line from $INPUT and appends it to the $OUTPUT file
#
poll() {
if [ ! -f "$CMD" ] ; then
echo "$CMD does not exist" 1>&2
exit 1
fi
if [ ! -x "$CMD" ] ; then
echo "$CMD is not executable" 1>&2
exit 1
fi
head -1 "$INPUT" >> "$OUTPUT" && sed -i '1d' "$INPUT"
ENTRY="`tail -1 "$OUTPUT"`"
$("$CMD" "$ENTRY")
}
#
# offer() appends the given arguments to the $INPUT file
#
offer() {
for arg in ${@:2} ; do
if [ -f "$arg" ] ; then
echo "$arg"
echo "$arg" >> "$INPUT"
fi
done
}
#
# peek() prints the next entry in the queue
#
peek() {
head -1 "$INPUT"
}
#
# random() passes a random line from $INPUT to $CMD
#
random() {
if [ ! -f "$CMD" ] ; then
echo "$CMD does not exist" 1>&2
exit 1
fi
if [ ! -x "$CMD" ] ; then
echo "$CMD is not executable" 1>&2
exit 1
fi
COUNT=`cat "$INPUT" | wc -l`
if [ "$COUNT" -lt 1 ] ; then
exit 0
fi
RANDOM_LINE_NO=$[ ( $RANDOM % $COUNT ) + 1 ]
RANDOM_LINE=`sed -n ''"$RANDOM_LINE_NO"'p' "$INPUT"`
$("$CMD" "$RANDOM_LINE")
}
print_help() {
cat << EOF
USAGE:
queue COMMAND
COMMANDS:
poll
removes the top line from \$INPUT and appends it to the \$OUTPUT file
offer
appends the given arguments to the \$INPUT file
peek
prints the next entry in the queue
random
passes a random line from \$INPUT to \$CMD
EXAMPLES:
To offer a list of files to the queue:
find /path/to/files | xargs ./queue.sh offer
EOF
}
if [ "$1" == "poll" ]
then
poll
elif [ "$1" == "offer" ]
then
offer $*
elif [ "$1" == "peek" ]
then
peek
elif [ "$1" == "random" ]
then
random
else
print_help
exit 1
fi
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