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Chapter 13 A Miscellany of Scripts |
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Chapter 13 A Miscellany of Scripts |
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Contributed by Tom Van Raalte
I thought you might want to use the following script around the office. It is a preprocessor for lpr that sends output to the "best" printer. [This shell script is written for a BSD or Linux system and you would use this command in place of lpr . It reads the output of the lpq command to determine if a specific printer is available. If not, it tries a list of printers to see which one is available or which is the least busy. Then it invokes lpr to send the job to that printer.]
#!/bin/sh # #set up temp file TMP=/tmp/printsum.$$ LASERWRITER=${LASERWRITER-ps6} #Check to see if the default printer is free? # # FREE=`lpq -P$LASERWRITER | awk ' { if ($0 == "no entries") { val=1 print val exit 0 } else { val=0 print val exit 0 } }'` #echo Free is $FREE # #If the default is free then $FREE is set, and we print and exit. # if [ $FREE -eq 1 ] then SELECT=$LASERWRITER #echo selected $SELECT lpr -P$SELECT $* exit 0 fi #echo Past the exit # #Now we go on to see if any of the printers in bank are free. # BANK=${BANK-$LASERWRITER} #echo bank is $BANK # #If BANK is the same as LASERWRITER, then we have no choice. #otherwise, we print on the one that is free, if any are free. # if [ "$BANK" = "$LASERWRITER" ] then SELECT=$LASERWRITER lpr -P$SELECT $* exit 0 fi #echo past the check bank=laserprinter # #Now we check for a free printer. #Note that $LASERWRITER is checked again in case it becomes free #during the check. # #echo now we check the other for a free one for i in $BANK $LASERWRITER do FREE=`lpq -P$i | awk ' { if ($0 == "no entries") { val=1 print val exit 0 } else { val=0 print val exit 0 } }'` if [ $FREE -eq 1 ] then # echo in loop for $i SELECT=$i # echo select is $SELECT # if [ "$FREE" != "$LASERWRITER" ] # then # echo "Output redirected to printer $i" # fi lpr -P$SELECT $* exit 0 fi done #echo done checking for a free one # #If we make it here then no printers are free. So we #print on the printer with the least bytes queued. # # for i in $BANK $LASERWRITER do val=`lpq -P$i | awk ' BEGIN { start=0; } /^Time/ { start=1; next; } (start == 1){ test=substr($0,62,20); print test; } ' | awk ' BEGIN { summ=0; } { summ=summ+$1; } END { print summ; }'` echo "$i $val" >> $TMP done SELECT=`awk '(NR==1) { select=$1; best=$2 } ($2 < best) { select=$1; best=$2} END { print select } ' $TMP ` #echo $SELECT # rm $TMP #Now print on the selected printer #if [ $SELECT != $LASERWRITER ] #then # echo "Output redirected to printer $i" #fi lpr -P$SELECT $* trap 'rm -f $TMP; exit 99' 2 3 15
For the most part, we've avoided scripts like these in which most of the logic is coded in the shell script. However, such a minimalist approach is representative of a wide variety of uses of awk. Here, awk is called to do only those things that the shell script can't do (or do as easily). Manipulating the output of a command and performing numeric comparisons is an example of such a task.
As a side note, the trap statement at the end should be at the top of the script, not at the bottom.
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| 13.7 gent - Get a termcap Entry |
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13.9 transpose - Perform a Matrix Transposition |
