Question: I like to make GDB set a break point when a variable equal some value I set, I tried this example:

```
#include <stdio.h>
main()
{ 
     int i = 0;
     for(i=0;i<7;++i)
        printf("%d\n", i);

     return 0;
}

```

Output from GDB:

```
(gdb) break if ((int)i == 5)
No default breakpoint address now.
(gdb) run
Starting program: /home/SIFE/run 
0
1
2
3
4
5
6

Program exited normally.
(gdb)

```

Like you see, GDB didn't make any break point, is this possible with GDB?

Answer: 
in addition to a watchpoint nested inside a breakpoint
you can also set a single breakpoint on the 'filename:line\_number' and use a condition.
I find it sometimes easier.

```
(gdb) break iter.c:6 if i == 5
Breakpoint 2 at 0x4004dc: file iter.c, line 6.
(gdb) c
Continuing.
0
1
2
3
4

Breakpoint 2, main () at iter.c:6
6           printf("%d\n", i);

```

If like me you get tired of line numbers changing, you can add a label
then set the breakpoint on the label like so:

```
#include <stdio.h>
main()
{ 
     int i = 0;
     for(i=0;i<7;++i) {
       looping:
        printf("%d\n", i);
     }
     return 0;
}

(gdb) break main:looping if i == 5

```
There are hardware and software watchpoints. They are for reading and for writing a variable. You need to consult a tutorial:

<http://www.unknownroad.com/rtfm/gdbtut/gdbwatch.html>

To set a watchpoint, first you need to break the code into a place where the varianle i is present in the environment, and set the watchpoint.

`watch` command is used to set a watchpoit for writing, while `rwatch` for reading, and `awatch` for reading/writing.