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Full Discussion: Lock file creation
Top Forums Shell Programming and Scripting Lock file creation Post 302801187 by hanson44 on Wednesday 1st of May 2013 02:10:35 PM
Old 05-01-2013
I rewrote the script some to make more sense, as best I can tell.

The script does not create the lock file, because the -f test already proved the lockfile previously existed. So there is no point using echo > $LOCKFILE command, unless there is some special meaning to clearing the lock file.

Some other code segment must create the lock file in the first place. Your code segment just tests for the existence of the lock file, and takes action if it exists. The 2>&1 has no point here. It doesn't hurt, but is just extra.

A log file usually likes having a date for each entry.
Code:
LOCK_FILE="$LOG_DIR/${DBNAME}_MD.lock"

# check for lock file

if [ -f "$LOCK_FILE" ]; then
  date >> "$LOG_FILE"
  echo "Lock file already exists: $LOCK_FILE" >> "$LOG_FILE"
  echo "Another process is running already. Will terminate this one." >> "$LOG_FILE"
  echo "If lock file not needed, please remove and reschedule job in cron." >> "$LOG_FILE"
  exit 0
fi

 

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LEARN ABOUT MINIX

ppmtosixel

ppmtosixel(1)                                                 General Commands Manual                                                ppmtosixel(1)

NAME

       ppmtosixel - convert a portable pixmap into DEC sixel format

SYNOPSIS

       ppmtosixel [-raw] [-margin] [ppmfile]

DESCRIPTION

       Reads  a  portable  pixmap  as input.  Produces sixel commands (SIX) as output.  The output is formatted for color printing, e.g. for a DEC
       LJ250 color inkjet printer.

       If RGB values from the PPM file do not have maxval=100, the RGB values are rescaled.  A printer control header and a color assignment table
       begin the SIX file.  Image data is written in a compressed format by default.  A printer control footer ends the image file.

OPTIONS

       -raw   If  specified,  each  pixel  will  be explicitly described in the image file.  If -raw is not specified, output will default to com-
              pressed format in which identical adjacent pixels are replaced by "repeat pixel" commands.  A raw file is often an order  of  magni-
              tude larger than a compressed file and prints much slower.

       -margin
              If  -margin  is not specified, the image will be start at the left margin (of the window, paper, or whatever).  If -margin is speci-
              fied, a 1.5 inch left margin will offset the image.

PRINTING

       Generally, sixel files must reach the printer unfiltered.  Use the lpr -x option or cat filename > /dev/tty0?.

BUGS

       Upon rescaling, truncation of the least significant bits of RGB values may result in poor color conversion.  If the original PPM maxval was
       greater  than  100,  rescaling  also reduces the image depth.  While the actual RGB values from the ppm file are more or less retained, the
       color palette of the LJ250 may not match the colors on your screen.  This seems to be a printer limitation.

SEE ALSO

       ppm(5)

AUTHOR

       Copyright (C) 1991 by Rick Vinci.

                                                                   26 April 1991                                                     ppmtosixel(1)
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