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io.h
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The following functions, macros, and classes are provided in io.h:

Topics

Name | Description
_findclose | Header File io.h Category Directory Control Routines Prototype int _findclose(long handle); Description Closes the specified search handle and releases associated resources associated with previous calls to findfirst/findnext. The handle parameter is the search handle returned by the previous call to _findfirst. This function is provided for Microsoft compatibility. Return Value On success, returns 0. Otherwise, returns –1 and sets errno to: ENOENTFile specification that could not be matched Portability
_findfirst, __wfindfirst | Header File io.h, wchar.h Category Directory Control Routines Prototype long _findfirst(char *filter, struct _finddata_t *fileinfo); long __wfindfirst(wchar_t *filter, struct _wfinddata_t *fileinfo); Description Begins a search of a disk directory to find information about the first instance of a filename that matches a specified filter. The filter parameter is a string that specifies which files to return. Wildcards may be used in the filter. The fileinfo parameter is the file information buffer. If a matching file is found, the fileinfo structure is filled with the file-directory information. These functions are provided for Microsoft compatibility. Return Value On success, returns a unique... more
_findfirsti64, _wfindfirsti64 | Header File io.h, wchar.h Category Directory Control Routines Prototype long _findfirsti64(char *filter, struct _finddatai64_t *fileinfo); long _wfindfirsti64(wchar_t *filter, struct _wfinddatai64_t *fileinfo); Description Begins a search of a disk directory to find information about the first instance of a filename that matches a specified filter. The filter parameter is a string that specifies which files to return. Wildcards may be used in the filter. The fileinfo parameter is the file information buffer. If a matching file is found, the fileinfo structure is filled with the file-directory information. These i64 versions are for 64 bit filesize use and are provided for Microsoft... more
_findnext, __wfindnext | Header File io.h, wchar.h Category Directory Control Routines Prototype long _findnext(long handle, struct _finddata_t *fileinfo); long __wfindnext(long handle, struct _wfinddata_t *fileinfo); Description Finds subsequent files, if any, that match the filter argument in a previous call to _findfirst/__wfindfirst. Then, _findnext/__wfindnext updates the fileinfo structure with the necessary information for continuing the search. One file name for each call to _tfindnext is returned until no more files are found in the directory matching the pathname (filter). The handle parameter is the search handle returned by a previous call to _findfirst. The fileinfo parameter is the file information buffer. These functions are... more
_findnexti64, _wfindnexti64 | Header File io.h, wchar.h Category Directory Control Routines Prototype long _findnexti64(long handle, struct _finddatai64_t *fileinfo); __int64 _wfindnexti64(long handle, struct _wfinddata_t *fileinfo); Description Finds subsequent files, if any, that match the filter argument in a previous call to _findfirsti64/_wfindfirsti64. Then, _findnexti64/_wfindnexti64 updates the fileinfo structure with the necessary information for continuing the search. One file name for each call to _tfindnext is returned until no more files are found in the directory matching the pathname (filter). The handle parameter is the search handle returned by a previous call to _findfirst. The fileinfo parameter is the file information buffer. These i64 versions... more
_get_osfhandle | Header File io.h Category Input/output Routines Prototype long _get_osfhandle(int filehandle); Description Associates file handles. The _get_osfhandle function associates an operating system file handle with an existing runtime file handle. The variable filehandle is the file handle of your program. Return value On success, _get_osfhandle returns an operating system file handle corresponding to the variable filehandle. On error, the function returns -1 and sets the global variable errno to
_open_osfhandle | Header File io.h Category Input/output Routines Prototype int _open_osfhandle(long osfhandle, int flags); Description Associates file handles. The _open_osfhandle function allocates a runtime file handle and sets it to point to the operating system file handle specified by osfhandle. The value flags is a bitwise OR combination of one or more of the following manifest constants (defined in fcntl.h):
_rtl_chmod, _wrtl_chmod | Header File io.h Category Input/output Routines Prototype int _rtl_chmod(const char *path, int func [, int attrib]); int _wrtl_chmod(const wchar_t *path, int func, ... ); Description Gets or sets file attributes. Note: The _rtl_chmod function replaces _chmod which is obsolete_rtl_chmod can either fetch or set file attributes. If func is 0, _rtl_chmod returns the current attributes for the file. If func is 1, the attribute is set to attrib. attrib can be one of the following symbolic constants (defined in dos.h):
_rtl_close | Header File io.h Category Input/output Routines Prototype int _rtl_close(int handle); Description Closes a file. Note: This function replaces _close which is obsolete The _rtl_close function closes the file associated with handle, a file handle obtained from a call to creat, creatnew, creattemp, dup, dup2, open, _rtl_creat, or _rtl_open. It does not write a Ctrl-Z character at the end of the file. If you want to terminate the file with a Ctrl-Z, you must explicitly output one. Return Value On success, _rtl_close returns 0. On error (if it fails because handle is not the handle of a valid, open file), _rtl_close... more
_rtl_creat, _wrtl_creat | Header File io.h Category Input/output Routines Prototype int _rtl_creat(const char *path, int attrib); int _wrtl_creat(const wchar_t *path, int attrib); Description Creates a new file or overwrites an existing one. Note: The _rtl_creat function replaces _creat, which is obsolete_rtl_creat opens the file specified by path. The file is always opened in binary mode. Upon successful file creation, the file pointer is set to the beginning of the file. The file is opened for both reading and writing. If the file already exists its size is reset to 0. (This is essentially the same as deleting the file and creating a new... more
_rtl_open, _wrtl_open | Header File io.h Category Input/output Routines Prototype int _rtl_open(const char *filename, int oflags); int _wrtl_open(const wchar_t *path, int oflags); Description Opens a file for reading or writing. Note: The _rtl_open function replaces _open which is obsolete. _rtl_open opens the file specified by filename, then prepares it for reading or writing, as determined by the value of oflags. The file is always opened in binary mode. oflags uses the flags from the following two lists. Only one flag from List 1 can be used (and one must be used) and the flags in List 2 can be used in any logical... more
_rtl_read | Header File io.h Category Input/output Routines Prototype int _rtl_read(int handle, void *buf, unsigned len); Description Reads from file. Note: This function replaces _read which is obsolete. This function reads len bytes from the file associated with handle into the buffer pointed to by buf. When a file is opened in text mode, _rtl_read does not remove carriage returns. The argument handle is a file handle obtained from a creat, open, dup, or dup2 call. On disk files, _rtl_read begins reading at the current file pointer. When the reading is complete, it increments the file pointer by the number of bytes... more
_rtl_write | Header File io.h Category Input/output Routines Prototype int _rtl_write(int handle, void *buf, unsigned len); Description Writes to a file. Note: This function replaces _write which is obsolete. _rtl_write attempts to write len bytes from the buffer pointed to by buf to the file associated with handle. The maximum number of bytes that _rtl_write can write is UINT_MAX -1 (because UINT_MAX is the same as -1), which is the error return indicator for _rtl_write. UINT_MAX is defined in limits.h. _rtl_write does not translate a linefeed character (LF) to a CR/LF pair because all its files are binary files. If the number... more
access, _waccess | Header File io.h Category Input/output Routines Prototype int access(const char *filename, int amode); int _waccess(const wchar_t *filename, int amode); Description Determines accessibility of a file. access checks the file named by filename to determine if it exists, and whether it can be read, written to, or executed. The list of amode values is as follows:
chmod, _wchmod | Header File io.h Category Input/output Routines Prototype int chmod(const char *path, int amode); int _wchmod(const wchar_t *path, int amode); Description Changes file access mode. chmod sets the file-access permissions of the file given by path according to the mask given by amode. path points to a string. amode can contain one or both of the symbolic constants S_IWRITE and S_IREAD (defined in sys\stat.h).
chsize | Header File io.h Category Input/output Routines Prototype int chsize(int handle, long size); Description Changes the file size. chsize changes the size of the file associated with handle. It can truncate or extend the file, depending on the value of size compared to the file's original size. The mode in which you open the file must allow writing. If chsize extends the file, it will append null characters (\0). If it truncates the file, all data beyond the new end-of-file indicator is lost. Return Value On success, chsize returns 0. On failure, it returns -1 and the global variable errno is... more
close | Header File io.h Category Input/output Routines Prototype int close(int handle); Description Closes a file. The close function closes the file associated with handle, a file handle obtained from a call to creat, creatnew, creattemp, dup, dup2, open, _rtl_creat, or _rtl_open. It does not write a Ctrl-Z character at the end of the file. If you want to terminate the file with a Ctrl-Z, you must explicitly output one. Return Value Upon successful completion, close returns 0. On error (if it fails because handle is not the handle of a valid, open file), close returns a value of -1 and the... more
_creat, _wcreat | Header File io.h Category Input/output Routines Prototype int creat(const char *path, int amode); int _wcreat(const wchar_t *path, int amode); Description Creates a new file or overwrites an existing one. Note: Remember that a backslash in a path requires '\\'. creat creates a new file or prepares to rewrite an existing file given by path. amode applies only to newly created files. A file created with creat is always created in the translation mode specified by the global variable _fmode (O_TEXT or O_BINARY). If the file exists and the write attribute is set, creat truncates the file to a length of... more
creatnew | Header File io.h Category Input/output Routines Prototype int creatnew(const char *path, int mode); Description Creates a new file. creatnew is identical to _rtl_creat with one exception: If the file exists, creatnew returns an error and leaves the file untouched. The mode argument to creatnew can be zero or an OR-combination of any one of the following constants (defined in dos.h):
creattemp | Header File io.h Category Input/output Routines Prototype int creattemp(char *path, int attrib); Description Creates a unique file in the directory associated with the path name. A file created with creattemp is always created in the translation mode specified by the global variable _fmode (O_TEXT or O_BINARY). path is a path name ending with a backslash (\). A unique file name is selected in the directory given by path. The newly created file name is stored in the path string supplied. path should be long enough to hold the resulting file name. The file is not automatically deleted when the program... more
dup | Header File io.h Category Input/output Routines Prototype int dup(int handle); Description Duplicates a file handle. dup creates a new file handle that has the following in common with the original file handle: Same open file or device Same file pointer (that is, changing the file pointer of one changes the other) Same access mode (read, write, read/write) handle is a file handle obtained from a call to creat, open, dup, dup2, _rtl_creat, or _rtl_open. Return Value Upon successful completion, dup returns the new file handle, a nonnegative integer; otherwise, dup returns -1. In the event of error, the global variable... more
dup2 | Header File io.h Category Input/output Routines Prototype int dup2(int oldhandle, int newhandle); Description Duplicates a file handle (oldhandle) onto an existing file handle (newhandle). dup2 creates a new file handle that has the following in common with the original file handle: Same open file or device Same file pointer (that is, changing the file pointer of one changes the other) Same access mode (read, write, read/write) dup2 creates a new handle with the value of newhandle. If the file associated with newhandle is open when dup2 is called, the file is closed. newhandle and oldhandle are file handles obtained from... more
eof | Header File io.h Category Input/output Routines Prototype int eof(int handle); Description Checks for end-of-file. eof determines whether the file associated with handle has reached end-of-file. Return Value If the current position is end-of-file, eof returns the value 1; otherwise, it returns 0. A return value of -1 indicates an error; the global variable errno is set to
filelength | Header File io.h Category Input/output Routines Prototype long filelength(int handle); Description Gets file size in bytes. filelength returns the length (in bytes) of the file associated with handle. Return Value On success filelength returns a long value the file length in bytes. On error it returns -1 and the global variable errno is set to
getftime, setftime | Header File io.h Category Input/output Routines Prototype int getftime(int handle, struct ftime *ftimep); int setftime(int handle, struct ftime *ftimep); Description Gets and sets the file date and time. getftime retrieves the file time and date for the disk file associated with the open handle. The ftime structure pointed to by ftimep is filled in with the file's time and date. setftime sets the file date and time of the disk file associated with the open handle to the date and time in the ftime structure pointed to by ftimep. The file must not be written to after the setftime call... more
isatty | Header File io.h Category Input/output Routines Prototype int isatty(int handle); Description Checks for device type. isatty determines whether handle is associated with any one of the following character devices: a terminal a console a printer a serial port Return Value If the device is one of the four character devices listed above, isatty returns a nonzero integer. If it is not such a device, isatty returns 0. Example
lock | Header File io.h Category Input/output Routines Prototype int lock(int handle, long offset, long length); Description Sets file-sharing locks. lock provides an interface to the operating system file-sharing mechanism. A lock can be placed on arbitrary, nonoverlapping regions of any file. A program attempting to read or write into a locked region will retry the operation three times. If all three retries fail, the call fails with an error. Return Value lock returns 0 on success. On error, lock returns -1 and sets the global variable errno to
locking | Header File io.h, sys\locking.h Category Input/output Routines Prototype int locking(int handle, int cmd, long length); Description Sets or resets file-sharing locks. locking provides an interface to the operating system file-sharing mechanism. The file to be locked or unlocked is the open file specified by handle. The region to be locked or unlocked starts at the current file position, and is length bytes long. Locks can be placed on arbitrary, nonoverlapping regions of any file. A program attempting to read or write into a locked region will retry the operation three times. If all three retries fail, the call fails with... more
lseek | Header File io.h Category Input/output Routines Prototype long lseek(int handle, long offset, int fromwhere); Description Moves file pointer. lseek sets the file pointer associated with handle to a new position offset bytes beyond the file location given by fromwhere. fromwhere must be one of the following symbolic constants (defined in io.h):
read | Header File io.h Category Input/output Routines Prototype int read(int handle, void *buf, unsigned len); Description Reads from file. read attempts to read len bytes from the file associated with handle into the buffer pointed to by buf. For a file opened in text mode, read removes carriage returns and reports end-of-file when it reaches a Ctrl-Z. The file handle handle is obtained from a creat, open, dup, or dup2 call. On disk files, read begins reading at the current file pointer. When the reading is complete, it increments the file pointer by the number of bytes read. On devices, the... more
setmode | Header File io.h Category Input/output Routines Prototype int setmode(int handle, int amode); Description Sets mode of an open file. setmode sets the mode of the open file associated with handle to either binary or text. The argument amode must have a value of either O_BINARY or O_TEXT, never both. (These symbolic constants are defined in fcntl.h.) Return Value setmode returns the previous translation mode if successful. On error it returns -1 and sets the global variable errno to
tell | Header File io.h Category Input/output Routines Prototype long tell(int handle); Description Gets the current position of a file pointer. tell gets the current position of the file pointer associated with handle and expresses it as the number of bytes from the beginning of the file. Return Value tell returns the current file pointer position. A return of -1 (long) indicates an error, and the global variable errno is set to
umask | Header File io.h, sys\stat.h Category Input/output Routines Prototype unsigned umask(unsigned mode); Description Sets file read/write permission mask. The umask function sets the access permission mask used by open and creat. Bits that are set in mode will be cleared in the access permission of files subsequently created by open and creat. The mode can have one of the following values, defined in sys\stat.h:
unlock | Header File io.h Category Input/output Routines Prototype int unlock(int handle, long offset, long length); Description Releases file-sharing locks. unlock provides an interface to the operating system file-sharing mechanism. unlock removes a lock previously placed with a call to lock. To avoid error, all locks must be removed before a file is closed. A program must release all locks before completing. Return Value On success, unlock returns 0 O error, it returns -1. Example
vsscanf | Header File io.h Category Memory and String Manipulation Routines Prototype int vsscanf(const char *buffer, const char *format, va_list arglist); Description Scans and formats input from a stream. The v...scanf functions are known as alternate entry points for the ...scanf functions. They behave exactly like their ...scanf counterparts, but they accept a pointer to a list of arguments instead of an argument list. Note: For details on format specifiers, see Scanf Format Specifiers. vsscanf scans a series of input fields, one character at a time, reading from a stream. Then each field is formatted according to a format specifier passed to... more
write | Header File io.h Category Input/output Routines Prototype int write(int handle, void *buf, unsigned len); Description Writes to a file. write writes a buffer of data to the file or device named by the given handle. handle is a file handle obtained from a creat, open, dup, or dup2 call. This function attempts to write len bytes from the buffer pointed to by buf to the file associated with handle. Except when write is used to write to a text file, the number of bytes written to the file will be no more than the number requested. The maximum number of... more

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