Reid
Thank you for the reply. I could use quotes or tics or backslash the
brackets. I have not encountered this problem before, where a file named
"1" would cause the problem and I am still curious as to why and how the
shell picked up the file name as apparently what is inside the brackets
doesn't seem to stop this odd behavior, I changed the inside to
[1,2,3,4,5] for example, but the program still crashed. I noticed that
[20,20,20,20,20] and [30,30,30,30,30] also works fine, apparently the
first two characters of "[1" trigger this reaction when the file "1"
exists in the local directory.
Randall
On 12/16/23 11:35, Reid wrote:
Sent with Proton Mail secure email.
On Saturday, December 16th, 2023 at 11:26 AM, American Citizen
<[email protected]> wrote:
Hello:
I bumped into a curious problem with the argv variables changing, when a
certain file named "1" is added into the local directory of the executable.
Here is the test file, a simple program named test.c
#include <stdio.h>
#include <string.h>
int main(int argc, char **argv) {
int i=1;
//int STDIN = 1;
char INCURV[1024] = {'\0'};
while(i<argc) {
if (!strcmp(argv[i],"-curve")) {
printf("we are here \n");
//strcpy(INCURV,argv[i+1]); STDIN=0; i+=2;
}
i+=1;
}
return 0;
}
I compile this file as
% gcc -o wack test.c -ggdb
(it is too easy to wipe out the source file if the object name almost
matches)
gcc is gcc version 7.5.0 (SUSE Linux)
I have the gdb debugger stop on line 13 "printf("we are here\n");"
Using input to the command:
% wack -arderivs -curve [0,0,0,-1156,0]
when no file named "1" exists in the directory then argv looks okay
argv[0] = "/../../wack"
argv[1] = "-arderivs"
argv[2] = "-curve"
argv[3] = "[0,0,0,-1156,0]"
argv[4] = 0x0
which is all fine and well.
I used the touch command to create file "1" in the local directory
% touch 1
and restart the gdb debugger.
argc count = 4 as expected
but argv[3] = "1"
Is this a bug in c?
Why is argv[3] changed?
It's a shell issue, not a C issue. The shell is interpreting something in the
square-bracketed argument as special characters. To avoid it, put the argument
in quotes.
(gdb) r -arderivs -curve 1
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /tmp/wack -arderivs -curve 1
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Demo:
(gdb) r -arderivs -curve [0,0,0,-1156,0]
...
Breakpoint 1, main (argc=4, argv=0x7fffffffd568) at test.c:6
6 int i=1;
(gdb) p argv[3]
$8 = 0x7fffffffd99f "1"
(gdb) r -arderivs -curve "[0,0,0,-1156,0]"
...
Breakpoint 1, main (argc=4, argv=0x7fffffffd558) at test.c:6
6 int i=1;
(gdb) p argv[3]
$9 = 0x7fffffffd991 "[0,0,0,-1156,0]"
Randall
