Filename Search Functions
The latest version of this topic can be found at Filename Search Functions.
These functions search for and close searches for specified file names:
Remarks
The _findfirst function provides information about the first instance of a file name that matches the file specified in the filespec argument. You can use in filespec any combination of wildcard characters that is supported by the host operating system.
The functions return file information in a _finddata_t structure, which is defined in IO.h. Various functions in the family use many variations on the _finddata_t structure. The basic _finddata_t structure includes the following elements:
unsigned attrib
File attribute.
time_t time_create
Time of file creation (–1L for FAT file systems). This time is stored in UTC format. To convert to the local time, use localtime_s.
time_t time_access
Time of the last file access (–1L for FAT file systems). This time is stored in UTC format. To convert to the local time, use localtime_s.
time_t time_write
Time of the last write to file. This time is stored in UTC format. To convert to the local time, use localtime_s.
_fsize_t size
Length of the file in bytes.
char name[ _MAX_PATH]
Null-terminated name of matched file or directory, without the path.
In file systems that do not support the creation and last access times of a file, such as the FAT system, the time_create and time_access fields are always –1L.
_MAX_PATH is defined in Stdlib.h as 260 bytes.
You cannot specify target attributes (such as _A_RDONLY) to limit the find operation. These attributes are returned in the attrib field of the _finddata_t structure and can have the following values (defined in IO.h). Users should not rely on these being the only values possible for the attrib field.
_A_ARCH
Archive. Set whenever the file is changed and cleared by the BACKUP command. Value: 0x20.
_A_HIDDEN
Hidden file. Not generally seen with the DIR command, unless you use the /AH option. Returns information about normal files and files that have this attribute. Value: 0x02.
_A_NORMAL
Normal. File has no other attributes set and can be read or written to without restriction. Value: 0x00.
_A_RDONLY
Read-only. File cannot be opened for writing and a file that has the same name cannot be created. Value: 0x01.
_A_SUBDIR
Subdirectory. Value: 0x10.
_A_SYSTEM
System file. Not ordinarily seen with the DIR command, unless the /A or /A:S option is used. Value: 0x04.
_findnext finds the next name, if any, that matches the filespec argument specified in an earlier call to _findfirst. The fileinfo argument should point to a structure initialized by the previous call to _findfirst. If a match is found, the fileinfo structure contents are changed as described earlier. Otherwise, it is left unchanged. _findclose closes the specified search handle and releases all associated resources for both _findfirst and _findnext. The handle returned by either _findfirst or _findnext must first be passed to _findclose, before modification operations, such as deleting, can be performed on the directories that form the paths passed to them.
You can nest the _find functions. For example, if a call to _findfirst or _findnext finds the file that is a subdirectory, a new search can be initiated with another call to _findfirst or _findnext.
_wfindfirst and _wfindnext are wide-character versions of _findfirst and _findnext. The structure argument of the wide-character versions has the _wfinddata_t data type, which is defined in IO.h and in Wchar.h. The fields of this data type are the same as those of the _finddata_t data type, except that in _wfinddata_t the name field is of type wchar_t instead of type char. Otherwise _wfindfirst and _wfindnext behave identically to _findfirst and _findnext.
_findfirst and _findnext use the 64-bit time type. If you must use the old 32-bit time type, you can define _USE_32BIT_TIME_T. The versions of these functions that have the 32 suffix in their names use the 32-bit time type, and those with the 64 suffix use the 64-bit time type.
Functions _findfirst32i64, _findnext32i64, _wfindfirst32i64, and _wfindnext32i64 also behave identically to the 32-bit time type versions of these functions except they use and return 64-bit file lengths. Functions _findfirst64i32, _findnext64i32, _wfindfirst64i32, and _wfindnext64i32use the 64-bit time type but use 32-bit file lengths. These functions use appropriate variations of the _finddata_t type in which the fields have different types for the time and the file size.
_finddata_t is actually a macro that evaluates to _finddata64i32_t (or _finddata32_t if _USE_32BIT_TIME_T is defined). The following table summarizes the variations on _finddata_t:
| Structure | Time type | File size type |
|---|---|---|
_finddata_t, _wfinddata_t |
__time64_t |
_fsize_t |
_finddata32_t, _wfinddata32_t |
__time32_t |
_fsize_t |
__finddata64_t, __wfinddata64_t |
__time64_t |
__int64 |
_finddata32i64_t, _wfinddata32i64_t |
__time32_t |
__int64 |
_finddata64i32_t, _wfinddata64i32_t |
__time64_t |
_fsize_t |
_fsize_t is a typedef for unsigned long (32 bits).
Example
// crt_find.c
// This program uses the 32-bit _find functions to print
// a list of all files (and their attributes) with a .C extension
// in the current directory.
#include <stdio.h>
#include <stdlib.h>
#include <io.h>
#include <time.h>
int main( void )
{
struct _finddata_t c_file;
intptr_t hFile;
// Find first .c file in current directory
if( (hFile = _findfirst( "*.c", &c_file )) == -1L )
printf( "No *.c files in current directory!\n" );
else
{
printf( "Listing of .c files\n\n" );
printf( "RDO HID SYS ARC FILE DATE %25c SIZE\n", ' ' );
printf( "--- --- --- --- ---- ---- %25c ----\n", ' ' );
do {
char buffer[30];
printf( ( c_file.attrib & _A_RDONLY ) ? " Y " : " N " );
printf( ( c_file.attrib & _A_HIDDEN ) ? " Y " : " N " );
printf( ( c_file.attrib & _A_SYSTEM ) ? " Y " : " N " );
printf( ( c_file.attrib & _A_ARCH ) ? " Y " : " N " );
ctime_s( buffer, _countof(buffer), &c_file.time_write );
printf( " %-12s %.24s %9ld\n",
c_file.name, buffer, c_file.size );
} while( _findnext( hFile, &c_file ) == 0 );
_findclose( hFile );
}
}
Listing of .c files
RDO HID SYS ARC FILE DATE SIZE
--- --- --- --- ---- ---- ----
N N N Y blah.c Wed Feb 13 09:21:42 2002 1715
N N N Y test.c Wed Feb 06 14:30:44 2002 312