Converting a DOS batch file to a shell script

Converting a DOS batch file to a shell script

Quite a few programmers who learn scripts on a PC are running DOS. In fact, the Disabled DOS batch file language can also write some powerful scripts, although they generally need to rely on external tools. So, at some point, we still need to convert old DOS batch files into Unix shell scripts. In general, it is not difficult to do this because the DOS batch file operation is simply a restricted subset of the equivalent shell script.

table L-1. batch file keywords/variables/operators, and equivalent shell symbols

Batch file Operators	shell script equivalence symbol	meaning
%	$	Command line parameter prefix
/	-	Command option Tag
\	/	Directory path delimiter
==	=	(equals) string comparison test
!==!	!=	(unequal) string comparison test
|	|	Pipeline
@	Set +v	Do not print the current command
*	*	File name "wildcard character"
>	>	File Redirection (Overwrite)
>>	>>	File Redirection (additional)
<	<	REDIRECT StdIn
%var%	$VAR	Environment variables
Rem	#	Comments
Not	!	Take counter
NUL	/dev/null	"Black Hole" to block command output
ECHO	Echo	Print (More options in bash)
ECHO.	Echo	Print Blank Lines
ECHO OFF	Set +v	Do not print subsequent commands
For%%var in (LIST) does	for var in [list]; Do	"for" loop
: LABEL	No equivalents (superfluous)	Label
Goto	No equivalents (using functions)	Jump to another location in the script
PAUSE	Sleep	Pause or wait for some time
CHOICE	Case or select	Menu selection
IF	If	If condition statement
IF EXIST FILENAME	If [-e filename]	Test whether the file exists
IF!%n==!	If [-Z "$N"]	Whether the parameter "N" exists
Pager	The source command or. (dot operator)	"include" another script
Command/c	The source command or. (dot operator)	"include" another script (same as Call)
SET	Export	Setting an environment variable
SHIFT	Shift	Move left command-line argument list
SGN	-lt or-GT	(shaping) symbols
ERRORLEVEL	$?	Exit status
CON	Stdin	"Console" (stdin)
PRN	/dev/lp0	(general) Printing equipment
LPT1	/dev/lp0	First printing device
COM1	/dev/ttys0	First serial port

Batch files generally contain DOS commands. We have to convert it to UNIX's equivalent command so we can convert the batch file to a shell script file.

table L-2. DOS command and UNIX equivalent command

DOS command	UNIX equivalent command	effect
ASSIGN	ln	Link file or directory
ATTRIB	chmod	Modify file Permissions
Cd	Cd	Change Directory
CHDIR	Cd	Change Directory
Cls	Clear	Clear Screen
COMP	diff, Comm, CMP	File comparison
COPY	Cp	File copy
Ctl-c	Ctl-c	Interrupt (signal)
Ctl-z	Ctl-d	EOF (end of file)
Del	Rm	deleting files
deltree	Rm-rf	Recursively delete a directory
DIR	Ls-l	Listing Directory Contents
ERASE	Rm	deleting files
EXIT	Exit	Exiting the current process
Fc	Comm, CMP	File comparison
FIND	Grep	Find a string in a file
Md	Mkdir	New Catalog
Mkdir	Mkdir	New Catalog
More	More	displaying text files on a paginated page
MOVE	Mv	Moving files
PATH	$PATH	Path to the executable file
REN	Mv	Rename (move)
RENAME	Mv	Rename (move)
RD	RmDir	Delete Directory
RMDIR	RmDir	Delete Directory
SORT	Sort	Sort files
Time	Date	Show System time
TYPE	Cat	Output files to stdout
Xcopy	Cp	(extended) file copy

In fact, almost all UNIX and shell operators, as well as commands, have many options, and they are much more powerful than DOS and batch files. Many DOS batch files need to rely on assistive tools, such as Ask.com, which is a similar copy of a lot worse than the read command. Dos for File name wildcard extension support is very limited, and is not complete, just identify * and ?.

Converting a DOS batch file to a SEHLL script is usually a simple matter, and the result of the conversion is usually better than the original batch file.

example L-1. VIEWDATA. Bat:dos Batch processing files

1 rem VIEWDATA 2 3 rem inspiration comes from the example "DOS POWERTOOLS" 4 REM PAUL Somerson write 5 6 7 @ECHO OFF 8 9 IF!%1==! GOTO VIEWDATA REM If there are no command line arguments ... FIND "%1" C:\BOZO\BOOKLIST. TXT EXIT0 The REM prints out a string that matches the line and then exits. 15:viewdata-C:\BOZO\BOOKLIST TYPE. TXT | More The REM displays the entire file, one page at a time. 19:exit0

Some improvements have been made to the conversion script.

example L-2. viewdata.sh: Shell script converted from Viewdata.bat

1 #!/bin/bash 2 # viewdata.sh 3 # Convert shell script from Viewdata.bat. 4 5 datafile=/home/bozo/datafiles/book-collection.data 6 argno=1 7 8 # @ECHO off This command is not needed here. 9 If [$#-lt "$ARGNO"] # if!%1==! GOTO VIEWDATA and then $DATAFILE # TYPE C:\MYDIR\BOOKLIST. TXT | More than (else) grep "$" $DATAFILE # FIND "%1" C:\MYDIR\BOOKLIST. TXT-Fi + exit 0 #: EXIT0 # jumps, tags, and other small tricks that you don't need in a shell script. we can say that the converted script is much better than the original batch file, 21 #+ It is shorter, looks neater and more elegant.

Ted Davis ' shell Scripts on the PC site has many tutorials on old-fashioned batch file programming, and some of the ingenious techniques he uses are similar to shell scripts.

Convert a DOS batch file to a shell script