Converting DOS Batch Files to Shell Scripts
Quite 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 H-1. Batch file keywords / variables / operators, and their shell equivalents | Batch File Operator | Shell Script Equivalent | Meaning |
|---|
| % | $ | command-line parameter prefix | | / | - | command option flag | | \ | / | directory path separator | | == | = | (equal-to) string comparison test | | !==! | != | (not equal-to) string comparison test | | | | | | pipe | | @ | set +v | do not echo current command | | * | * | filename "wild card" | | > | > | file redirection (overwrite) | | >> | >> | file redirection (append) | | < | < | redirect stdin | | %VAR% | $VAR | environmental variable | | REM | # | comment | | NOT | ! | negate following test | | NUL | /dev/null | "black hole" for burying command output | | ECHO | echo | echo (many more option in Bash) | | ECHO. | echo | echo blank line | | ECHO OFF | set +v | do not echo command(s) following | | FOR %%VAR IN (LIST) DO | for var in [list]; do | "for" loop | | :LABEL | none (unnecessary) | label | | GOTO | none (use a function) | jump to another location in the script | | PAUSE | sleep | pause or wait an interval | | CHOICE | case or select | menu choice | | IF | if | if-test | | IF EXIST FILENAME | if [ -e filename ] | test if file exists | | IF !%N==! | if [ -z "$N" ] | if replaceable parameter "N" not present | | CALL | source or . (dot operator) | "include" another script | | COMMAND /C | source or . (dot operator) | "include" another script (same as
CALL) | | SET | export | set an environmental variable | | SHIFT | shift | left shift command-line argument list | | SGN | -lt or -gt | sign (of integer) | | ERRORLEVEL | $? | exit status | | CON | stdin | "console" (stdin) | | PRN | /dev/lp0 | (generic) printer device | | LPT1 | /dev/lp0 | first printer device | | COM1 | /dev/ttyS0 | first serial port |
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 H-2. DOS Commands and Their UNIX Equivalents | DOS Command | UNIX Equivalent | Effect |
|---|
| ASSIGN | ln | link file or directory | | ATTRIB | chmod | change file permissions | | CD | cd | change directory | | CHDIR | cd | change directory | | CLS | clear | clear screen | | COMP | diff, comm, cmp | file compare | | COPY | cp | file copy | | Ctl-C | Ctl-C | break (signal) | | Ctl-Z | Ctl-D | EOF (end-of-file) | | DEL | rm | delete file(s) | | DELTREE | rm -rf | delete directory recursively | | DIR | ls -l | directory listing | | ERASE | rm | delete file(s) | | EXIT | exit | exit current process | | FC | comm, cmp | file compare | | FIND | grep | find strings in files | | MD | mkdir | make directory | | MKDIR | mkdir | make directory | | MORE | more | text file paging filter | | MOVE | mv | move | | PATH | $PATH | path to executables | | REN | mv | rename (move) | | RENAME | mv | rename (move) | | RD | rmdir | remove directory | | RMDIR | rmdir | remove directory | | SORT | sort | sort file | | TIME | date | display system time | | TYPE | cat | output file to stdout | | XCOPY | cp | (extended) file copy |
| 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 H-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 H-2. viewdata.sh: Shell Script Conversion of VIEWDATA.BAT #!/bin/bash
# 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" $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. |
