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Top Forums Programming What is use of "char __user *buf"? Post 302836985 by kg_gaurav on Thursday 25th of July 2013 02:30:45 AM
Old 07-25-2013
Question What is use of "char __user *buf"?

I have seen several function containing "char __user *buf" as parameter.
this is disturbing my basic knowledge of c

the basic syntax says
char *buf means buf is a pointer which points to a char

now what does
char __user *buf means?


Please reply
 

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getwd(3C)																 getwd(3C)

NAME
getwd() - get pathname of current working directory SYNOPSIS
DESCRIPTION
places the absolute pathname of the current working directory in the array pointed to by buf, and returns buf. If the length of the pathname of the current working directory is greater than bytes, fails and returns a null pointer. RETURN VALUE
Upon successful completion, returns a pointer to the current directory pathname. Otherwise, it returns NULL with set. ERRORS
fails if the following condition is encountered: The length of the specified path name exceeds bytes, or the length of a component of the path name exceeds bytes while is in effect. may fail if any of the following conditions are encountered: Read or search permission is denied for a component of pathname. buf points outside the allocated address space of the process. may not always detect this error. EXAMPLES
#include <stdio.h> #include <unistd.h> char *cwd; char buf[PATH_MAX+1]; ... if ((cwd = getwd(buf)) == NULL) { perror("getwd"); exit(1); } puts(cwd); WARNINGS
For portability, is preferred over this function. AUTHOR
was developed by HP and the University of California, Berkeley. SEE ALSO
getcwd(3C), thread_safety(5). STANDARDS CONFORMANCE
getwd(3C)
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