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Full Discussion: Bash script
Top Forums Shell Programming and Scripting Bash script Post 302518203 by ddreggors on Thursday 28th of April 2011 11:17:05 PM
Old 04-29-2011
Quote:
using while loop to run till the number is postive ie <!= 0
If I understand you correctly what you want is to increment a number until it reaches above 0?

but the code you offered as your attempt will only loop in the while "$a" is already greater than or equal to 0:

Code:
a=0
 while [ "$a" -ge 0  ]

Then since "$a" is instantiated as 0 and it matches the first while condition you start incrementing "$a":

Code:
a=$(($a+1))

after that increment you are testing if "$a" is less than or equal to 0 and break out of the while loop if it is:

Code:
if [ "$a" -le 0 ]
  then
    break
  fi

Essentially you do this:

1. Set $a = 0
2. Test is $a is equal or grater than zero
3. Increment $a by 1 (making it now $a=1)
4. Test for it to be 0 or less and break if it is
5. echo $a
6. Restart while loops with $a equal to 1

This will never break as $a will always be 0 or greater which means it will evaluate to true in the while condition and then it will just echo numbers to screen growing by 1 each time forever (or until you manually kill it).


Try this instead:

Code:
#!/bin/bash
a=0
CURR_MIN=$(date +%M |tr -d '0')
BREAK_MIN=$(($CURR_MIN + 1))
while [ "$a" -eq 0 ]
do
  # Set a predictable condition,
  # anything that will change
  # like the minute in the current time
  # (date +%M)
  CURR_MIN=$(date +%M |tr -d '0')
  if [ $CURR_MIN -ge $BREAK_MIN  ]
  then
    a=$(($a+1))
  fi
  echo -e "\$a: $a\nBREAK_MIN: $BREAK_MIN\nCURR_MIN: $CURR_MIN\n-------------------"
done

echo -e "\n\n\n"
exit 0

Now obviously we could just have easily placed a break inside that if statement instead of increment $a. The point was to show a valid way to break if $a is not 0 though.
 

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LEARN ABOUT DEBIAN

voice_set_playmode

voice_set_playmode(3alleg4)					  Allegro manual				       voice_set_playmode(3alleg4)

NAME

       voice_set_playmode - Adjusts the loop status of the specified voice. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       void voice_set_playmode(int voice, int playmode);

DESCRIPTION

       Adjusts the loop status of the specified voice. This can be done while the voice is playing, so you can start a sample in looped mode (hav-
       ing set the loop start and end positions to the appropriate values), and then clear the loop flag when you want to  end	the  sound,  which
       will  cause it to continue past the loop end, play the subsequent part of the sample, and finish in the normal way. The mode parameter is a
       bitfield containing the following values:

       PLAYMODE_PLAY

       Plays the sample a single time. This is the default if you don't set the loop flag.

       PLAYMODE_LOOP

       Loops repeatedly through the sample, jumping back to the loop start position upon reaching the loop end.

       PLAYMODE_FORWARD

       Plays the sample from beginning to end. This is the default if you don't set the backward flag.

       PLAYMODE_BACKWARD

       Reverses the direction of the sample. If you combine this with the loop flag, the sample jumps to the loop end position upon  reaching  the
       loop start (ie. you do not need to reverse the loop start and end values when you play the sample in reverse).

       PLAYMODE_BIDIR

       When  used  in  combination  with  the  loop flag, causes the sample to change direction each time it reaches one of the loop points, so it
       alternates between playing forwards and in reverse.

SEE ALSO

Allegro 							   version 4.4.2				       voice_set_playmode(3alleg4)
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