Programming

I´m writing this program in QNX , I`m kinda new to UNIX and programing in general, and when I try to run it it gives me the Memory Fault error. Can anyone help?

Code:

#include <stdio.h>
#include <fcntl.h>
void main(void)
{int a[1],ter;
 char buf[12];
 printf("a=");
scanf("%d",a);
ter=open ("/dev/ttpy1",O_WRONLY);
sprintf(buf,"%s",a[1]);
write(ter,a,sizeof(a));
close(ter);
}

Its supposed to print the scanned string in to a second terminal window (ttpy1), so I open the two terminals before running the program but it gives me the Memory error.

for starters:

Code:

sprintf(buf,"%s",a[1]);

should be "%d" not "%s". This causes the printf code to interpret the variable as a nul-terminated string. It keeps reading the "string" byte-by-byte until it finds ascii 0, nul.
If it reads past the end of the stack, boom.

Thanks it still doesn't print anything on ttpy1 but at least it doesn't crash anymore xD

Check the return value of write(). Check the return value of everything, really.

I don't want to correct everything....

main is NOT void, it is int. Return to int from main(). Always.

Turn on warnings and every other diagnostic known to the compiler.

Strings in C cannot be less than two characters, if they contain dat. a[1] will not fly generally. Why? they need a terminating nul characters \0 == ascii 0

you do not have all of the #include files required to compile the code.
Read the man page for read & open - it tells you at the top the name of the include file(s)required.

You cannot call a compile ok until:
1. there are zero warnings
2. there are zero errors

Period. Anything else that seems to work is a disaster waiting to happen.

hmm I can compile it with 0 warnings and 0 errors, with int instead of void and adding return 0 at the end and with %d instead of %s, the only problem I have now is that it doesn't print on the second terminal window ttyp1so i think my problem is this line :
ter=open ("/dev/ttpy1",O_WRONLY);

Professor numnuts at college told us that terminals are treated like files and are "mounted" in the /dev/ directory.

As for the missing .h as I said before a have 0 errors so i don`t think that`s the problem, just to be sure I added iostream and fstream .h, and i got invalid library errors on both when I tried to compile.

I am "programing" using a normal text editor and writing in the terminal

#cc program.c -o program

You're doing sprintf to buf but writing the original variable "a" which contains the binary representation of the number.

Change

Code:

write(ter,a,sizeof(a));

to

Code:

write(ter,buf,strlen(buf));

Note to use strlen instead of sizeof so you don't write the unused portion of the array to the terminal.

Also, as Corona said, you should be checking return values from all of the library calls. For example, if, for some reason, you cannot open the tty, ter would contain -1. Do things like

Code:

if (ter < 0) { perror("open tty"); exit(errno); }