Please read the man page more carefully
getline is included in OS X (at least it is in Lion, that page may have been from 'the old days')
From a Terminal type 'man getline'
Code:
NAME
getdelim, getline -- get a line from a stream
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <stdio.h>
ssize_t
getdelim(char ** restrict linep, size_t * restrict linecapp, int delimiter,
FILE * restrict stream);
ssize_t
getline(char ** restrict linep, size_t * restrict linecapp, FILE * restrict stream);
EXAMPLES
The following code fragment reads lines from a file and writes them to standard output. The
fwrite() function is used in case the line contains embedded NUL characters.
char *line = NULL;
size_t linecap = 0;
ssize_t linelen;
while ((linelen = getline(&line, &linecap, fp)) > 0)
fwrite(line, linelen, 1, stdout);
Per the man page, it looks like your first two arguments to the function are not right.
You are correct about the first two arguments being wrong, but some of the later suggestions are also wrong.
Getline() can use a buffer supplied by the caller, or it can allocate a buffer and return it to the caller. If the user supplies a buffer, it must be a malloc'd buffer (not a fixed char array) since it may need to be realloc'd if the line is longer than the supplied buffer. It's probably easier to let getline() allocate the buffer. You indicate this by passing in the address of a NULL pointer.
The docs say that getline() wants a char**, the address of a buffer pointer, and a size_t *, the address of a buffer length variable. It will read the line and update the buffer pointer to point at the new line buffer (which it has allocated) and set the capacity variable to the length of the buffer it has allocated. These are both output variables from getline(), so it needs the address of the caller's variables so it can update them.
Code:
getline(&line, &linecap, fp)
In the example code they pass the address of the local variables line and linecap. Note that the line variable was initialized to NULL before calling getline(). Getline() will allocate a buffer, read the line, and return the length of the line it read (or an error code). Before returning it will update the caller's buffer pointer and buffer length variables.
Once getline() has allocated a buffer, that same buffer can be passed back in to subsequent calls where its contents will be overwritten.
To prevent a memory leak the allocated buffer must be free'd by the caller when it is done with it. This isn't done in the example code, but there should be a free(line) call after the loop ends.
HTH
Dennis Cote
