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Appendix L. Converting DOS Batch Files to Shell ScriptsQuite a number of programmers learned scripting on a PC running DOS. Even the crippled DOS batch file language allowed writing some fairly powerful scripts and applications, though they often required extensive kludges and workarounds. Occasionally, the need still arises to convert an old DOS batch file to a UNIX shell script. This is generally not difficult, as DOS batch file operators are only a limited subset of the equivalent shell scripting ones. Table L-1. Batch file keywords / variables / operators, and their shell equivalents
Batch files usually contain DOS commands. These must be translated into their UNIX equivalents in order to convert a batch file into a shell script. Table L-2. DOS commands and their UNIX equivalents
Note Virtually all UNIX and shell operators and commands have many more options and enhancements than their DOS and batch file equivalents. Many DOS batch files rely on auxiliary utilities, such as ask.com, a crippled counterpart to read. DOS supports a very limited and incompatible subset of filename wildcard expansion, recognizing only the * and ? characters. Converting a DOS batch file into a shell script is generally straightforward, and the result ofttimes reads better than the original. Example L-1. VIEWDATA.BAT: DOS Batch File REM VIEWDATA REM INSPIRED BY AN EXAMPLE IN "DOS POWERTOOLS" REM BY PAUL SOMERSON @ECHO OFF IF !%1==! GOTO VIEWDATA REM IF NO COMMAND-LINE ARG... FIND "%1" C:\BOZO\BOOKLIST.TXT GOTO EXIT0 REM PRINT LINE WITH STRING MATCH, THEN EXIT. :VIEWDATA TYPE C:\BOZO\BOOKLIST.TXT | MORE REM SHOW ENTIRE FILE, 1 PAGE AT A TIME. :EXIT0 The script conversion is somewhat of an improvement. Example L-2. viewdata.sh: Shell Script Conversion of VIEWDATA.BAT #!/bin/bash # viewdata.sh # Conversion of VIEWDATA.BAT to shell script. DATAFILE=/home/bozo/datafiles/book-collection.data ARGNO=1 # @ECHO OFF Command unnecessary here. if [ $# -lt "$ARGNO" ] # IF !%1==! GOTO VIEWDATA then less $DATAFILE # TYPE C:\MYDIR\BOOKLIST.TXT | MORE else grep "1ドル" $DATAFILE # FIND "%1" C:\MYDIR\BOOKLIST.TXT fi exit 0 # :EXIT0 # GOTOs, labels, smoke-and-mirrors, and flimflam unnecessary. # The converted script is short, sweet, and clean, #+ which is more than can be said for the original. Ted Davis' Shell Scripts on the PC site has a set of comprehensive tutorials on the old-fashioned art of batch file programming. Certain of his ingenious techniques could conceivably have relevance for shell scripts. |
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