DIRECTORY

Section: C Library Functions (3)
Index Return to Main Contents

BSD mandoc
BSD 4.2

NAME

opendir readdir telldir seekdir rewinddir closedir dirfd - directory operations

SYNOPSIS

Fd #include <sys/types.h> Fd #include <dirent.h> Ft DIR * Fn opendir const char *filename Ft struct dirent * Fn readdir DIR *dirp Ft long Fn telldir const DIR *dirp Ft void Fn seekdir DIR *dirp long loc Ft void Fn rewinddir DIR *dirp Ft int Fn closedir DIR *dirp Ft int Fn dirfd DIR *dirp

DESCRIPTION

The Fn opendir function opens the directory named by Fa filename , associates a directory stream with it and returns a pointer to be used to identify the directory stream in subsequent operations. The pointer NULL is returned if Fa filename cannot be accessed, or if it cannot malloc(3) enough memory to hold the whole thing.

The Fn readdir function returns a pointer to the next directory entry. It returns NULL upon reaching the end of the directory or detecting an invalid Fn seekdir operation.

The Fn telldir function returns the current location associated with the named directory stream

The Fn seekdir function sets the position of the next Fn readdir operation on the directory stream The new position reverts to the one associated with the directory stream when the Fn telldir operation was performed. Values returned by Fn telldir are good only for the lifetime of the DIR pointer, Fa dirp , from which they are derived. If the directory is closed and then reopened, the Fn telldir value may be invalidated due to undetected directory compaction. It is safe to use a previous Fn telldir value immediately after a call to Fn opendir and before any calls to Fn readdir .

The Fn rewinddir function resets the position of the named directory stream to the beginning of the directory.

The Fn closedir function closes the named directory stream and frees the structure associated with the Fa dirp pointer, returning 0 on success. On failure, -1 is returned and the global variable errno is set to indicate the error.

The Fn dirfd function returns the integer file descriptor associated with the named directory stream see open(2).

Sample code which searchs a directory for entry ``name'' is:

len = strlen(name);
dirp = opendir(".");
while ((dp = readdir(dirp)) != NULL)
        if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
                (void)closedir(dirp);
                return FOUND;
        }
(void)closedir(dirp);
return NOT_FOUND;

HISTORY

The Fn opendir , Fn readdir , Fn telldir , Fn seekdir , Fn rewinddir , Fn closedir , and Fn dirfd functions appeared in BSD 4.2