geoff@desint.UUCP (Geoff Kuenning) (02/01/88)
Summary:
/usr/bin/sdiff forces the -b switch on the user even if it's unwanted.
Problem:
/usr/bin/sdiff's "-o switch is a very useful tool for integrating
different branches of the same program. However, this utility is
limited by one questionable design decision. This is that
that sdiff invokes diff with the -b (ignore whitespace differences)
switch. This means that an integration of two pieces of code will
miss any changes in indentation.
Repeat-By:
Suppose file "sdtest1.c" contains:
a = b;
and file "sdtest2.c" has been changed to:
if (c == d)
a = b;
If you then execute the command:
sdiff -o sdtest3.c sdtest1.c sdtest2.c
and type "r" to the only prompt, you will get:
if (c == d)
a = b;
On the other hand, if you use:
sdiff -o sdtest3.c sdtest2.c sdtest1.c
and type "l" to the prompt, you will get a file identical to
sdtest2.c, as you should.
Fix:
The following context diff modifies sdiff to correct this problem,
plus a minor argument-processing oversight, and also allows you to
select an editor other than "ed" for use with the "e" command.
Problems corrected:
(1) sdiff always invoked diff with the -b switch, which hid some
differences that the user might consider important.
(2) The (erroneous) command "sdiff -o" caused a core dump on
no-NULL-dereference machines, instead of a usage message.
Improvements added:
(1) The "e" command now respects the EDITOR environment variable.
(2) There is now a "-e" switch which can be used to override the
default editor and the EDITOR environment variable.
(3) The "-b" and "-h" flags can now be passed on to diff.
Geoff Kuenning geoff@ITcorp.com {uunet,trwrb}!desint!geoff
Note: if you want to discuss this, please use mail, as I don't normally
read these newsgroups.
Index: sdiff.c
*** sdiff.c.old Sun Jan 31 14:53:35 1988
--- sdiff.c Sun Jan 31 14:53:41 1988
***************
*** 10,16
*/
! /* sdiff [-l] [-s] [-w #] [-o output] file1 file2
* does side by side diff listing
* -l leftside only for identical lines
* -s silent; only print differences
--- 10,17 -----
*/
! /* sdiff [-b] [-h] [-l] [-s] [-w #]
! * [-e editor] [-o output] file1 file2
* does side by side diff listing
* -b, -h are passed on to diff
* -l leftside only for identical lines
***************
*** 12,17
/* sdiff [-l] [-s] [-w #] [-o output] file1 file2
* does side by side diff listing
* -l leftside only for identical lines
* -s silent; only print differences
* -w # width of output
--- 13,19 -----
/* sdiff [-b] [-h] [-l] [-s] [-w #]
* [-e editor] [-o output] file1 file2
* does side by side diff listing
+ * -b, -h are passed on to diff
* -l leftside only for identical lines
* -s silent; only print differences
* -w # width of output
***************
*** 15,20
* -l leftside only for identical lines
* -s silent; only print differences
* -w # width of output
* -o output interactive creation of new output
commands:
s silent; do not print identical lines
--- 17,23 -----
* -l leftside only for identical lines
* -s silent; only print differences
* -w # width of output
+ * -e editor editor to use instead of 'ed' with -o option
* -o output interactive creation of new output
commands:
s silent; do not print identical lines
***************
*** 27,32
e call ed with empty file
q exit from program
* functions:
cmd decode diff commands
put1 output left side
--- 30,39 -----
e call ed with empty file
q exit from program
+ * If the EDITOR environment variable is defined and there is
+ * no '-e' switch, the value of EDITOR will be used as the
+ * default editor.
+
* functions:
cmd decode diff commands
put1 output left side
***************
*** 52,58
char BLANKS[100] = " ";
char GUTTER[WGUTTER] = " ";
! char *DIFF = "diff -b ";
char diffcmd[BMAX];
char inbuf[10];
--- 59,65 -----
char BLANKS[100] = " ";
char GUTTER[WGUTTER] = " ";
! char *DIFF = "diff ";
char diffcmd[BMAX];
char inbuf[10];
***************
*** 68,73
char *pgmname;
char *file1;
FILE *fdes1;
char buf1[BMAX+1];
--- 75,87 -----
char *pgmname;
+ char *bflag = ""; /* "-b " if -b switch specified */
+ char *hflag = ""; /* "-h " if -h switch specified */
+ char *editor; /* Editor to be invoked */
+ char *editname; /* Editor with pathname removed. Zero if editor has
+ switches or if the pathname is not absolute.
+ */
+
char *file1;
FILE *fdes1;
char buf1[BMAX+1];
***************
*** 105,110
char **argv;
{
extern onintr();
int com;
register int n1, n2, n;
--- 119,125 -----
char **argv;
{
extern onintr();
+ extern char *getenv(), *strrchr();
int com;
register int n1, n2, n;
***************
*** 116,121
signal(SIGPIPE,onintr);
if (signal(SIGTERM,SIG_IGN)!=SIG_IGN)
signal(SIGTERM,onintr);
pgmname = argv[0];
while(--argc>1 && **++argv == '-'){
switch(*++*argv){
--- 131,138 -----
signal(SIGPIPE,onintr);
if (signal(SIGTERM,SIG_IGN)!=SIG_IGN)
signal(SIGTERM,onintr);
+ if ((editor = getenv ("EDITOR")) == 0)
+ editor = "/bin/ed";
pgmname = argv[0];
while(--argc>1 && **++argv == '-'){
switch(*++*argv){
***************
*** 134,139
llen = LMAX;
break;
case 'l':
leftonly++;
break;
--- 151,164 -----
llen = LMAX;
break;
+ case 'b':
+ bflag = "-b ";
+ break;
+
+ case 'h':
+ hflag = "-h ";
+ break;
+
case 'l':
leftonly++;
break;
***************
*** 141,146
case 's':
silent++;
break;
case 'o':
oflag++;
argc--;
--- 166,179 -----
case 's':
silent++;
break;
+
+ case 'e':
+ if (argc > 0) {
+ argc--;
+ editor = *++argv;
+ }
+ break;
+
case 'o':
if (argc > 0) {
oflag++;
***************
*** 142,150
silent++;
break;
case 'o':
! oflag++;
! argc--;
! ofile = *++argv;
break;
default:
error("Illegal argument: %s",*argv);
--- 175,185 -----
break;
case 'o':
! if (argc > 0) {
! oflag++;
! argc--;
! ofile = *++argv;
! }
break;
default:
error("Illegal argument: %s",*argv);
***************
*** 151,157
}
}
if(argc != 2){
! fprintf(stderr,"Usage: sdiff [-l] [-s] [-o output] [-w #] file1 file2\n");
exit(2);
}
--- 186,192 -----
}
}
if(argc != 2){
! fprintf(stderr,"Usage: sdiff [-b] [-h] [-l] [-s] [-o output] [-e editor] [-w #] file1 file2\n");
exit(2);
}
***************
*** 155,160
exit(2);
}
file1 = *argv++;
file2 = *argv;
file1=filename(file1,file2);
--- 190,201 -----
exit(2);
}
+ if (editor[0] == '/'
+ && strrchr (editor, ' ') == 0 && strrchr (editor, '\t') == 0)
+ editname = strrchr (editor, '/') + 1;
+ else
+ editname = 0;
+
file1 = *argv++;
file2 = *argv;
file1=filename(file1,file2);
***************
*** 181,186
}
/* Call DIFF command */
strcpy(diffcmd,DIFF);
strcat(diffcmd,file1);
strcat(diffcmd," ");
strcat(diffcmd,file2);
--- 222,229 -----
}
/* Call DIFF command */
strcpy(diffcmd,DIFF);
+ strcat(diffcmd,hflag);
+ strcat(diffcmd,bflag);
strcat(diffcmd,file1);
strcat(diffcmd," ");
strcat(diffcmd,file2);
***************
*** 602,608
int (*oldintr) ();
! switch(pid=fork()){
case -1:
error("Cannot fork","");
--- 645,652 -----
int (*oldintr) ();
! if (editname) { /* Can we just exec the editor? */
! switch(pid=fork()){
case -1:
error("Cannot fork","");
***************
*** 604,614
switch(pid=fork()){
! case -1:
! error("Cannot fork","");
! case 0:
! execl("/bin/ed", "ed", file, 0);
! }
oldintr = signal(SIGINT, SIG_IGN); /*ignore interrupts while in ed */
while(pid != wait(&i))
--- 648,659 -----
if (editname) { /* Can we just exec the editor? */
switch(pid=fork()){
! case -1:
! error("Cannot fork","");
! case 0:
! execl(editor, editname, file, 0);
! error("Cannot exec '%s'", editor);
! }
/*ignore interrupts while in editor */
oldintr = signal(SIGINT, SIG_IGN);
***************
*** 610,619
execl("/bin/ed", "ed", file, 0);
}
! oldintr = signal(SIGINT, SIG_IGN); /*ignore interrupts while in ed */
! while(pid != wait(&i))
! ;
! signal(SIGINT,oldintr); /*restore previous interrupt proc */
}
char *filename(pa1, pa2)
--- 655,673 -----
error("Cannot exec '%s'", editor);
}
! /*ignore interrupts while in editor */
! oldintr = signal(SIGINT, SIG_IGN);
! while(pid != wait(&i))
! ;
! signal(SIGINT,oldintr); /*restore previous interrupt proc */
! } else { /* Can't exec, must use system () */
! char editcmd[BMAX];
!
! strcpy (editcmd, editor);
! strcat (editcmd, " ");
! strcat (editcmd, file);
! system (editcmd);
! }
}
char *filename(pa1, pa2)
--
Geoff Kuenning geoff@ITcorp.com {uunet,trwrb}!desint!geoff