How to print a null-terminated string with newlines without showing backslash escapes in gdb?

Question

I have a variable

char* x = "asd\nqwe\n ... "

and I want to print it with newlines printed as newlines not backslash n. Is it possible?

if nought else works, you can replace the '\n' with '\x0a' - this will the linefeed char directly. — slashmais, Oct 07 '09 at 10:35
Actually, I came here for a way to PRINT the \n >.> .. I was able to do this: print (char*)[nsstring cString] — Mazyod, Mar 19 '12 at 09:59

score 116 · Accepted Answer · edited Jul 21 '15 at 11:41

116

Update: Why not just use the gdb printf command?

(gdb) printf "%s", x
asd
qwe
...
(gdb)

Old answer: From within the debugger you can execute commands. Just call printf

(gdb) call printf("%s", x)
asd
qwe
...
(gdb)

edited Jul 21 '15 at 11:41

Anton Samsonov

answered Oct 07 '09 at 10:30

ezpz

I can't use stdout or stderr because these channels are attached to other program. – Łukasz Lew Oct 07 '09 at 10:37
9

Note that it's important to terminate the printf command with a /n if your char* doesn't already end with one. – Ben Flynn Sep 12 '12 at 23:24
1

Worth to note that `printf()` function call may succeed and return the number of characters in the string, but not actually output those characters on the screen; the same holds true for `puts()` function call and perhaps others of that kind. In contrast, the built-in `printf` command works as expected. – Anton Samsonov Jul 21 '15 at 10:46

score 36 · Answer 2 · edited Jan 08 '14 at 00:28

36

Use the string specifier:

print /s x

edited Jan 08 '14 at 00:28

Paul Richter

answered Jan 08 '14 at 00:06

netskink

4

This is definitely better than calling the debugged program's functions like `printf`, but may only work on relatively new versions of GDB: mine yields “Format letter "s" is meaningless in "print" command”, for example. – Anton Samsonov Jul 21 '15 at 10:33
5

This don't work when `x` is a variable other than address, in that case, need use `x` command, e.g `x/s x`, or need a type convert, e.g `p (char *) &x`. – Eric May 23 '16 at 07:36
3

This will not work when the string is larger than some length. It gets truncated when printing. printf method does print the full string. – sadashiv30 Aug 09 '17 at 18:16
1

when your string is in a buffer then "p/s (char *)buff" – RichieHH Nov 20 '20 at 05:02

2 Answers2