I thought if you open a file in text mode you can use '\n' which implicitly expands to the platform specific newline.
the below code never compares '\n' to be true. What's the easiest way to do such a comparison?
Code:FILE* istream = fopen("text.txt", "r"); while ( EOF != (c = fgetc(istream)) ) { if ( '\n' == c ) { puts("detected newline"); } }
Last edited by keira; 12-02-2007 at 12:29 PM.
Generally a newline will be one of the following:
- '\n' [*nix systems]
- '\r''\n' [Windows]
- '\r' [Mac]
Not to be annoying, but are you sure test.txt has any '\n' chars? Are you sure that istream isn't NULL before the loop?
No idea, it works well enough here
Did you get the right filename, in the right directory?Code:$ cat foo.c #include <stdio.h> int main(void) { FILE *istream = fopen("text.txt", "r"); int c; while (EOF != (c = fgetc(istream))) { if ('\n' == c) { puts("detected newline"); } } return (0); } $ gcc foo.c $ cat text.txt hello world $ ./a.exe detected newline detected newline
Did you check for a successful fopen() ?
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
I'm in win32 so its gotta be this '\r''\n' business MacGyver was talking about. Trust me everything else is good
But how do I do a comparison for '\r''\n'? Before I wrote this post I was about to write a function that takes in the FILE object and first checks for 0x0d (which is a CR) and then seeks ahead to the next byte to check for 0x0A (LF). But I'm hoping for a better solution lol.
Searching for '\n' should still work since every '\r''\n' contains a '\n'.
Again, I would check to make sure istream is not NULL before you start reading. That could very easily cause you to not get any newline chars to be registered.
Not a \r\n issue here.
Same code, different compiler.
Do exactly what I've done, and paste exactly what you see.Code:> cl -nologo foo.c foo.c > type text.txt hello world > foo.exe detected newline detected newline
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
To detect \r\n, if you need it:
Or a safer approach:Code:if (c == '\r' && fgetc(istream) == '\n') // newline detected
Code:if (c == '\r') { c = fgetc(istream); if (c == '\n') // newline detected }
alright '\n' does work. the hexidecimal revealed that there were hidden 0x09 ('\t')s right before the '\n' which was causing the issue. Thanks all for help!
but... if you have a '\n' in a switch statement is it different from if ( '\n' == nextChar ) ?
