bash help

[fdrake]

ok i have a problem with "if" condition:


#!/bin/bash

playerId="0";


if [ "$playerId" == "0" ];
then
echo "id is =empty"
else
echo "id is NOT empty"
fi

playerId=$(ps --ppid "$parent" | grep "mplayer" | cut -d " " -f 1);
#when i do echo $playerId i have always a number ex. 32812. so it's never empty

if [ "$playerId" == "0" ];
then
echo "id is =empty"
else
echo "id is NOT empty"
fi



why it keeps saying:

"id is =empty"
"id is =empty"

instead of:

"id is =empty"
"id is NOT empty"

must be something stupid but ....

[AlphaLexman]

ok i have a problem with "if" condition:


#!/bin/bash

playerId="0";


if [ "$playerId" == "0" ];
then
echo "id is =empty"
else
echo "id is NOT empty"
fi

playerId=$(ps --ppid "$parent" | grep "mplayer" | cut -d " " -f 1);
#when i do echo $playerId i have always a number ex. 32812. so it's never empty

if [ "$playerId" == "0" ];
then
echo "id is =empty"
else
echo "id is NOT empty"
fi



why it keeps saying:

"id is =empty"
"id is =empty"

instead of:

"id is =empty"
"id is NOT empty"

must be something stupid but ....

Where is the variable '$parent' set ??

[fdrake]

let me put the whole script maybe it's easier to understand



#!/bin/bash

#check if the input file has changed

file_t=$(ls -al input | cut -d " " -f 7)
file_t="$file_t";
echo "$file_t";

playerId="0"; #mplayer child PID
playerId="$playerId";

while :
do

file_n=$(ls -al input | cut -d " " -f 7)
file_n="$file_n"
echo "$file_n"; #check every 3 sec if the file "input" has been edited
if [ "$file_t" != "$file_n" ];
then
echo "input has changed!"
file_t=$file_n; #update the date of the "input" file


#check first if you have any mplayer process running previously. id yes kill the child first and then make new process.

if [ "$playerId" == "0" ];
then
echo "id is =empty"
else
echo "id is NOT empty"
kill -9 "$playerId"
fi


#This script executes every command line present in the input file (at the same time in the background)

cat input | while read line;
do

echo $line
($line | tee >> output) &

parent="$!";
playerId=$(ps --ppid "$parent" | grep "mplayer" | cut -d " " -f 1);
playerId="$playerId"
echo "$playerId";

done
else
:
fi
sleep 3
done.



my problem is that in the 2nd if the condition is always true. so that the child process never gets killed...

[fdrake]

ok i solved the problem, it wasn't the loop the problem but the variable.mys solution was to write the result of a con=mmand in a file and then import that data line by line into a variable.



#check first if you have any mplayer process running previously. kill the child first and then make new process.

cat ids | while read lineids;
do
kill -9 $lineids
done



#This script executes every command line present in the input file (at the same time in the background)

cat input | while read line;
do
echo $line
($line | tee >> output) &

parent="$!";
ps --ppid "$parent" | grep "mplayer" | cut -d " " -f 1 | tee >> ids;
echo "$(less ids)";
done
echo "playerid : $(less ids)";

else
:
fi
sleep 2
done

-- VISUAL -- 48,0-1 Bot