使用文件描述符读取文件

Question

I need to read a file opened like this:

int outfile = open(*fileName, "w");

using the file descriptor, I'm doing that like this:

char txt[50];
int bytes;  
bytes = read(outfile,txt, 50);

But I'm getting segmentation fault and the application abort, any ideas?

Answer 1

Note the second argument to open. It's "w" this seems like it should indicate that you're opening the file for writing. However, my man pages for open indicates that the second argument should be one of: O_RDONLY , O_WRONLY , or O_RDWR . (fopen uses strings like "w", "w+", "r", ... but that's fopen not open). You may be getting lucky that the value of "w" as an int sets you up for writing but you really want to check your return values and probably want to use

open(*filename, O_RDWR);

to set up the mode for reading and writing.