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HP-UX 11i Version 3: February 2007

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devnm — map device ID to file path


#include <devnm.h>

int devnm ( mode_t devtype, dev_t devid, char *path, size_t pathlen, int cache );


Given a device type, a device ID, and a string in which to return the result, devnm() maps the type and ID to a block or character special file (device file) name by searching /dev. It returns in path the full path name of the first special file encountered with a matching device type and ID. It searches /dev and all its subdirectories recursively in unspecified order.

The parameters are:


One of the file type values S_IFBLK or S_IFCHR documented in stat(5). Bits other than those in the S_IFMT set are ignored. Hence the value can be, for example, an st_mode value returned by stat() (see stat(2)).


A device ID (the combined major and minor numbers) such as returned by stat() in the st_dev or st_rdev field.


Pointer to the buffer in which to return the path name result.


Tells the available length of the path string, including the NUL terminator character. If path is too short to hold the full path name, only the first pathlen-1 characters are returned in a null-terminated string, and the return value is altered (see below).


A flag that tells devnm() whether to save file information in memory allocated by malloc(), and later, whether to use that saved information instead of searching /dev again. A subsequent call with cache non-zero can be much faster, especially if /dev is a large tree. However, the first call with cache true might be slower because devnm() must read all of the /dev tree once to create the cache, rather than returning immediately upon finding a matching file. Any call with cache set to zero ignores the cache, if any, and reads the directory.

To allow for possible future enhancements, cache should be restricted to the values 0 and 1.

There is no way to tell devnm() to free its cached memory.

devnm() ignores unreadable directories and files for which stat() fails.


devnm() returns one of the following values:


Successful. The result is in path.


ftw() failed. errno contains the value returned from ftw(). path might be altered if cache is set. If cache was set for the first time, devnm() freed any memory allocated by the current call.


No matching special file was found. errno is undefined. path is unaltered.


A matching special file was found, but the name was truncated to fit in path. errno is undefined.

If malloc() fails, devnm() silently abandons the attempt to do caching in the current or any later call with cache true, and frees any memory allocated by the current call.


devnm() was developed by HP.

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