FS

Overview

Provides functions for file system, include file operations, directory operations and so on.

Since:

1.0

Version:

1.0

Summary

Files

File Name Description
dirent.h Provides functions and structures used for performing file system operations, including file read/write, directory traversal, and file system mounting.
fcntl.h Declares structures and functions used for file and directory operations such as opening a file, creating a file, and allocating space.
ftw.h Provides functions and structures related to file tree traversal.
glob.h Provides functions and structures used to find path names matching a pattern and release the memory that was applied for during the search.
libgen.h Provides functions related to file management, for example, obtaining directory and file names.
ioctl.h Manipulates a device.
mount.h Provides functions for mounting and unmounting a file system.
stat.h Provides functions for file and directory operations.
statfs.h Provides a function to obtain information about a file system.
statvfs.h Provides a function and structure related to file system information operation, for example, viewing file system information.
utime.h Provides the function and structure used for setting file access time and modification time.

Data Structures

Data Structure Name Description
dirent Defines the content of the directory.
FTW Defines the file tree walker (FTW).
glob_t Defines the search information.
stat Defines the file information structure.
statvfs Describes file system information.
utimbuf Defines the file access time and modification time.

Macros

Macro Name and Value Description
O_ACCMODE    (03 O_SEARCH)
O_RDONLY    00 Read-only.
O_WRONLY    01 Write-only.
O_RDWR    02 Read and write.
fallocate64    fallocate Pre-allocates space to a file. See fallocate.
FTW_F    1 Regular file.
FTW_D    2 Directory.
FTW_DNR    3 Unreadable directory. Its subdirectories will not be traversed.
FTW_NS    4 The data of the stat structure cannot be obtained. The possible cause is that the permission is incorrect.
FTW_SL    5 Symbolic link.
FTW_DP   6
FTW_SLN    7 Symbolic link that names a non-existent file.
FTW_PHYS    1 Symbolic links that are not traversed. If not set, symbolic links are traversed by default.
FTW_MOUNT    2 Stay within the same file system.
FTW_CHDIR    4 chdir is called to go to the directory before reading the directory.
FTW_DEPTH    8 All subdirectories will be traversed before the directory itself.
GLOB_ERR    0x01 Return upon a read error.
GLOB_MARK    0x02 Append a slash (/) to each path, which corresponds to a directory.
GLOB_NOSORT    0x04 Do not sort the returned path names.
GLOB_DOOFFS    0x08 In the pglob parameter of the glob() function, reserve a string that has a length of pglob->gl_offs and ends with \0 at the beginning of the string list in pglob->pathv. That is, the newly matched string is appended to a position where the distance from the beginning of pglob->pathv is the length of pglob->gl_offs.
GLOB_NOCHECK    0x10 If no pattern matches, return the original pattern.
GLOB_APPEND    0x20 Append the results of this call to the results returned by a previous call to glob().
GLOB_NOESCAPE    0x40 Do not use a backslash () as an escape character.
GLOB_PERIOD    0x80 Allow a leading period to be matched by metacharacters.
GLOB_TILDE    0x1000 Carry out tilde expansion. If a tilde (~) is the only character in the pattern, or an initial tilde is followed immediately by a slash (/), then the home directory of the caller is substituted for the tilde.
GLOB_TILDE_CHECK    0x4000 Similar to GLOB_TILDE. The difference is that if the username is invalid, or the home directory cannot be determined, glob() returns GLOB_NOMATCH to indicate an error.
GLOB_NOSPACE    1 Memory insufficient.
GLOB_ABORTED    2 Read error.
GLOB_NOMATCH    3 No matching item is found.
GLOB_NOSYS    4 The function is not supported.

Typedefs

Typedef Name Description
DIR typedef struct __dirstream Opens the handle of the folder directory.

Functions

Function Name Description
closedir (DIR dirp) int Closes a specified directory.
opendir (const char dirname) DIR Opens a specified directory.
readdir (DIR dirp) struct dirent Reads a specified directory.
readdir_r (DIR restrict dirp, struct dirent *restrict entry, struct dirent __restrict result) int Reads a specified directory (thread-safe version).
rewinddir (DIR *dirp) void Resets a directory stream read position.
alphasort (const struct dirent a, const struct dirent b) int Sorts the directory entries in alphabetical order.
scandir (const char dir, struct dirent namelist, int(sel)(const struct dirent ), int(compar)(const struct dirent , const struct dirent )) int Scans directory to find the target entries.
seekdir (DIR dirp, long offset) void Sets the position of the next readdir call in the directory stream.
telldir (DIR dirp) long Obtains the current position in the specified directory stream.
creat (const char path, mode_t mode) int Creates a file or rewrites an existing file.
open (const char path, int oflags,…) int Opens a file.
fallocate (int fd, int mode, off_t offset, off_t len) int Pre-allocates space to a file.
fcntl (int fd, int cmd,…) int Manipulates a specified file descriptor.
ftw (const char path, int(fn)(const char file, const struct stat sb, int flag), int depth) int Traverses a file tree.
nftw (const char path, int(fn)(const char file, const struct stat sb, int flag, struct FTW s), int fd_limit, int flags) int Traverses a file tree.
glob (const char __restrict pattern, int flags, int(errfunc)(const char , int), glob_t restrict pglob) int Searches for path names that meet a specified pattern.
globfree (glob_t pglob) void Frees allocated memory from a call to glob().
dirname (char path) char Obtains a directory name in a specified path.
basename (char path) char Obtains a file name (excluding the directory) in a specified path.
ioctl (int fd, int cmd,…) int Manipulates a device.
mount (const char source, const char target, const char filesystemtype, unsigned long mountflags, const void data) int Mounts a file system.
umount (const char target) int Unmounts a file system.
umount2 (const char target, int flags) int Unmounts a file system.
stat (const char restrict path, struct stat __restrict buf) int Obtains file information.
fstat (int fd, struct stat buf) int Obtains file status information.
lstat (const char __restrict path, struct stat restrict buf) int Obtains file information.
mkdir (const char pathname, mode_t mode) int Creates a directory.
mkfifo (const char name, mode_t mode) int Creates a named pipe to implement inter-process communication.
mkdirat (int fd, const char pathname, mode_t mode) int Creates a directory.
chmod (const char pathname, mode_t mode) int Modifies permissions for a file.
umask (mode_t mode) mode_t Sets umask for a process.
statfs (const char path, struct statfs buf) int Obtains file system information of a file in a specified path.
statvfs (const char *restrict path, struct statvfs __restrict buf) int Obtains the file system information.
utime (const char filename, const struct utimbuf *times) int Sets the access time and modification time of a file.

Details

Macro Definition Documentation

FTW_DP


1. #define FTW_DP   6

Description:

@briefDirectory. All subdirectories in this directory have been traversed.

Function Documentation

alphasort()


1. int alphasort (const struct [dirent]($api-api-SmartVision-Devices-dirent.md) ** a, const struct [dirent]($api-api-SmartVision-Devices-dirent.md) ** b )

Description:

Sorts the directory entries in alphabetical order.

This function is used to sort the two directory entries passed through the input parameters in alphabetical order. Generally, these parameters are passed in scandir as its last parameter.

Parameters:

Name Description
a Indicates the pointer to directory entry a.
a Indicates the pointer to directory entry b.

Returns:

Returns an integer greater than, equal to, or less than 0, respectively, based on whether the name of the directory entry to which a points is lexically greater than, equal to, or less than the directory.

basename()


1. char* basename (char * path)

Description:

Obtains a file name (excluding the directory) in a specified path.

Parameters:

Name Description
path Indicates the pointer to the path.

Returns:

Returns the file name if the operation is successful; returns NULL otherwise.

chmod()


1. int chmod (const char * pathname, mode_t mode )

Description:

Modifies permissions for a file.

Parameters:

Name Description
pathname Indicates the pointer to the path of the file.
mode Indicates the new file permission.

Attention:

This function can be used only in the JFFS2 file system.

Returns:

Returns 0 if the operation is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL The pathname is a null pointer or an empty string.
EACCES The permission bit of the file mode does not allow the requested access, or the search permission is denied on the path prefix directory.
EFAULT Incorrect IP address.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOENT The directory component in the path name does not exist.
ENOMEM Insufficient memory.
ENOTDIR A component of the path prefix is the name of an existing file. The file is neither a directory nor a symbolic link of a directory.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EROFS The physical drive is write-protected.
EEXIST The file or directory already exists.
ENOSYS The function is not supported.

closedir()


1. int closedir ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) * dirp)

Description:

Closes a specified directory.

Parameters:

Name Description
dirp Indicates the pointer to the structure representing the directory to close.

Returns:

Returns 0 if the directory is successfully closed; returns -1 and sets errno to the following value otherwise.

errno Description
EBADF dirp is not a valid opened directory stream.

creat()


1. int creat (const char * path, mode_t mode )

Description:

Creates a file or rewrites an existing file.

Parameters:

Name Description
path Indicates the pointer to the name of the file to create or rewrite.
mode Indicates permissions on the file.

Returns:

Returns 0 if the file is created or rewritten successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL path points to an invalid path.
ENAMETOOLONG The length of path is greater than the value of NAME_MAX.
ENXIO Invalid inode or the inode is not a mount point.
EMFILE All file descriptors that can be used by the process are opened.
EPERM The file structure corresponding to the file descriptor cannot be obtained.
EACCES Access denied by the permission bit of file mode
ENOMEM The memory is insufficient.
ENODEV The device does not exist.
EEXIST O_CREAT and O_EXCL are set.
EIO A hardware error occurs at the low-level disk I/O layer. As a result, the physical drive cannot work.
ENFILE The number of opened files in the system has reached the maximum.
ENOTDIR A component of the path prefix is the name of an existing file and is not a directory.
EBUSY The operation is rejected according to the file sharing policy.
ENOTEMPTY The directory is not empty.
ELOOP Too many symbolic links are encountered.
EFAULT The IP address is incorrect.

dirname()


1. char* dirname (char * path)

Description:

Obtains a directory name in a specified path.

Parameters:

Name Description
path Indicates the pointer to the path.

Returns:

Returns the directory name if the operation is successful; returns NULL otherwise.

fallocate()


1. int fallocate (int fd, int mode, off_t offset, off_t len )

Description:

Pre-allocates space to a file.

Parameters:

Name Description
fd Indicates the file descriptor.
mode Indicates the operation mode. Only FALLOC_FL_KEEP_SIZE is supported.
offset Indicates the offset of the file to allocate.
len Indicates the size of the disk space to be allocated to the file.

Attention:

This function can be used only in the FAT file system.

Returns:

Returns 0 if the operation is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL The value of len or offset is less than 0 or greater than that of INT_MAX, or the value of mode is not FALLOC_FL_KEEP_SIZE.
EBADF fd is not a valid file descriptor, or the basic file system does not support this operation.
EAGAIN The file list is null.
EACCES Access denied by the authority bit of file mode
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
EPERM The operation is not allowed or the access is rejected.
EBUSY The operation is rejected according to the file sharing policy.

fcntl()


1. int fcntl (int fd, int cmd,  ... )

Description:

Manipulates a specified file descriptor.

Parameters:

Name Description
fd Indicates the file descriptor.
cmd Indicates the command used to manipulate the file descriptor.
cmd Description
F_DUPFD Copy a new file descriptor (fd is a file).
F_GETFL Obtain the status of the file specified by fd. (fd is a file or sockets are available.)
F_SETFL Set the file descriptor status. (fd is a file or sockets are available.)

Returns:

Returns the value depending on cmd if the operation is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EAGAIN The operation is prohibited.
EBADF fd is an invalid file descriptor.
EFAULT Beyond the accessible address space.
EINVAL The command specified by cmd cannot be recognized.
ENOLCK Too many segment locks open, lock table is full, or a remote locking protocol failed.
EPERM Attempt to clear the O_APPEND flag on a file that has the append-only attribute set.

fstat()


1. int fstat (int fd, struct [stat]($api-api-SmartVision-Devices-stat.md) * buf )

Description:

Obtains file status information.

Parameters:

Name Description
fd Indicates the file descriptor.
buf Indicates the pointer to a stat structure into which file information is placed.

Returns:

Returns 0 if file information is obtained successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EBADF fd is an invalid file descriptor.
EAGAIN The file list is null.
EINVAL Invalid parameter.
ENOENT A component of path does not name an existing file or path is an empty string.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOMEM Insufficient memory.
ENOSYS The function is not supported.
EACCES Search permission is denied on a component of the path prefix.
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
ENOSPC No available space on the device.
EISDIR The named file is a directory.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EBUSY The operation is rejected according to the file sharing policy.
EPROTO The protocol in NFS is incorrect.
ENODEV No such device.
EFAULT Incorrect IP address.

ftw()


1. int ftw (const char * path, int(*)(const char *file, const struct [stat]($api-api-SmartVision-Devices-stat.md) *sb, int flag) fn, int depth )

Description:

Traverses a file tree.

This function is used to traverse a file tree for search.

Parameters:

Name Description
path Indicates the pointer to the file directory to traverse.
fn Indicates the pointer to the function to be called for the found entry. For the fn function, file identifies the path of the file relative to path, and sb indicates the pointer to the stat structure. flag indicates the flag. The values of flag are as follows:
depth Indicates the number of files that can be opened during traversal.
value Description
FTW_F Regular file
FTW_D Directory
FTW_DNR Unreadable directory. Its subdirectories will not be traversed.
FTW_SL Symbolic link
FTW_NS The data of the stat structure cannot be obtained. The possible cause is that the permission is incorrect.

Returns:

Returns 0 if the tree is traversed; returns the value that is returned by the fn() function if the traversal is interrupted; returns -1 if an error occurs.

glob()


1. int glob (const char *__restrict pattern, int flags, int(*)(const char *, int) errfunc, [glob_t]($api-api-SmartVision-Devices-glob_t.md) *__restrict pglob )

Description:

Searches for path names that meet a specified pattern.

Parameters:

Name Description
pattern Indicates the pattern you want to match.
flags Indicates the matching mode.
errfunc Indicates the pointer to the error processing callback function. If errfunc is not a null pointer, errfunc() is called when an error occurs (opendir(), readdir(), or stat() fails) during the search. If the function returns a non-zero value or GLOB_ERR is set, glob() terminates the entire search process.
pglob Indicates the pointer to the address storing the matched path names.
flags Description
GLOB_ERR GLOB_ERR
GLOB_MARK GLOB_MARK
GLOB_NOSORT GLOB_NOSORT
GLOB_DOOFFS GLOB_DOOFFS
GLOB_NOCHECK GLOB_NOCHECK
GLOB_APPEND GLOB_APPEND
GLOB_NOESCAPE GLOB_NOESCAPE
GLOB_PERIOD GLOB_PERIOD
GLOB_TILDE GLOB_TILDE
GLOB_TILDE_CHECK GLOB_TILDE_CHECK

Returns:

Returns 0 on successful completion; returns GLOB_NOSPACE for running out of memory; returns GLOB_ABORTED for a read error; returns GLOB_NOMATCH for no match found.

globfree()


1. void globfree ([glob_t]($api-api-SmartVision-Devices-glob_t.md) * pglob)

Description:

Frees allocated memory from a call to glob().

Parameters:

Name Description
pglob Indicates the pointer to the address of memory dynamically allocated for a glob call.

ioctl()


1. int ioctl (int fd, int cmd,  ... )

Description:

Manipulates a device.

This function is used to perform specified operations on an input device file descriptor.

Parameters:

Name Description
fd Indicates the file descriptor of the device (file-related file descriptors are not supported).
cmd Indicates the operation instruction for the device. You can define it based on the specific device.

Returns:

Returns 0 if the operation is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EBADF fd is an invalid file descriptor.
EFAULT An inaccessible memory area is referenced.
EINVAL The command request is invalid.
ENOTTY fd is not associated with a character special device.

lstat()


1. int lstat (const char *__restrict path, struct [stat]($api-api-SmartVision-Devices-stat.md) *__restrict buf )

Description:

Obtains file information.

Parameters:

Name Description
path Indicates the file path.
buf Indicates the pointer to a stat structure into which file information is placed.

Returns:

Returns 0 if file information is obtained successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL Invalid parameter.
ENOENT A component of path does not name an existing file or path is an empty string.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOMEM Insufficient memory.
ENOSYS The function is not supported.
EAGAIN The file list is null.
EACCES The permission bit of the file mode does not allow the requested access, or the search permission is denied on the path prefix component.
EEXIST The file or directory already exists.
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
ENOSPC No available space on the device.
ENFILE The number of opened files in the system has reached the maximum.
ENOTEMPTY The directory is not empty.
EISDIR The named file is a directory.
ENOTDIR A component of the path prefix is the name of an existing file. The file is neither a directory nor a symbolic link of a directory.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EBUSY The operation is rejected according to the file sharing policy.
EPROTO The protocol in NFS is incorrect.
ENODEV No such device.
EFAULT Incorrect IP address.

mkdir()


1. int mkdir (const char * pathname, mode_t mode )

Description:

Creates a directory.

Parameters:

Name Description
pathname Indicates the pointer to the name of the directory to create.
mode Indicates the directory permission.

Attention:

This function can NOT be used in the PROC file system.

Returns:

Returns 0 if the directory is created successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL The pathname is a null pointer or an empty string.
EACCES The permission bit of the file mode does not allow the requested access, or the search permission is denied on the path prefix directory.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOENT The directory component in the path name does not exist.
EEXIST The file or directory already exists.
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
ENOSPC No available space on the device.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EBUSY The operation is rejected according to the file sharing policy.
ENOSYS The function is not supported.
EPROTO The protocol in NFS is incorrect.
EFAULT Incorrect IP address.

mkdirat()


1. int mkdirat (int fd, const char * pathname, mode_t mode )

Description:

Creates a directory.

Parameters:

Name Description
fd Indicates the file descriptor of the target directory. (Currently, only AT_FDCWD is supported.)
pathname Indicates the pointer to the name of the directory to create.
mode Indicates the directory permission.

Attention:

This function can NOT be used in the PROC file system.

Returns:

Returns 0 if the directory is created successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL The pathname is a null pointer or an empty string.
EACCES The permission bit of the file mode does not allow the requested access, or the search permission is denied on the path prefix directory.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOENT The directory component in the path name does not exist.
EEXIST The file or directory already exists.
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
ENOSPC No available space on the device.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EBUSY The operation is rejected according to the file sharing policy.
ENOSYS The function is not supported.
EPROTO The protocol in NFS is incorrect.
EFAULT Incorrect IP address.

mkfifo()


1. int mkfifo (const char * name, mode_t mode )

Description:

Creates a named pipe to implement inter-process communication.

Parameters:

Name Description
name Indicates the pointer to the name of the pipe to create.
mode Not supported.

Attention:

Permission control is not supported. The number of pipes that can be created is not limited. Pipes can be created only in the /dev directory.

Returns:

Returns 0 if the pipe is created successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL Invalid input parameter (for example, empty address, file name too long or the file is not in the /dev directory).
EEXIST The file already exists.
ENOMEM Insufficient memory.

mount()


1. int mount (const char * source, const char * target, const char * filesystemtype, unsigned long mountflags, const void * data )

Description:

Mounts a file system.

Mounts a device (referenced by a file system name) to a specified directory.

Parameters:

Name Description
source Indicates the pointer to the device to mount.
target Indicates the pointer to the path of the mount point.
filesystemtype Indicates the pointer to the file system type.
mountflags Indicates the mounting flag.
data Indicates the pointer to the mounting data.

Returns:

Returns 0 if the mounting is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EACCES A component of the path was not searchable.
EBUSY source is already mounted.
EFAULT One of the pointer parameters points outside the user address space.
EINVAL source cannot be mounted.
ELOOP Too many links encountered during path name resolution.
EMFILE (Non-block device) Virtual device table is full.
ENAMETOOLONG The path name length is greater than the value of MAXPATHLEN.
ENODEV No such file system type is configured in the kernel.
ENOENT A path name is null or has a nonexistent component.
ENOMEM Insufficient memory.
ENOTBLK source is not a block device.
ENOTDIR target or the prefix of source is not a directory.
ENGIO No such device.
EPERM No permission.

nftw()


1. int nftw (const char * path, int(*)(const char *file, const struct [stat]($api-api-SmartVision-Devices-stat.md) *sb, int flag, struct [FTW]($api-api-SmartVision-Devices-FTW.md) *s) fn, int fd_limit, int flags )

Description:

Traverses a file tree.

This function is used to traverse a file tree. It has a similar effect to ftw except that it takes an additional parameter flags.

Parameters:

Name Description
path Indicates the pointer to the file directory to traverse.
fn Indicates the pointer to the function to be called for the found entry. For the fn function, file identifies the path of the file relative to path, and sb indicates the pointer to the stat structure. flag indicates the flag. The values of flag are as follows: The fourth argument of fn() is a pointer to a FTW structure.
fd_limit Indicates the number of files that can be opened during traversal.
flags Indicates the traversal action. It is a bitwise inclusive-OR of zero or more of the following flags:
value Description
FTW_F Regular file
FTW_D Directory
FTW_DNR Unreadable directory. Its subdirectories will not be traversed.
FTW_SL Symbolic link
FTW_NS The data of the stat structure cannot be obtained. The possible cause is that the permission is incorrect.
FTW_DP Directory. All subdirectories have been traversed.
FTW_SLN Symbolic link that names a non-existent file

Returns:

Returns 0 if the tree is traversed; returns the value that is returned by the fn() function if the traversal is interrupted; returns -1 if an error occurs.

open()


1. int open (const char * path, int oflags,  ... )

Description:

Opens a file.

Parameters:

Name Description
path Indicates the pointer to the name of the file to open.
oflags Indicates the file access mode. Available values are as follows:
oflags Description
O_RDONLY Read-only
O_WRONLY Write-only
O_RDWR Read and write
O_APPEND If set, the file offset will be set to the end of the file prior to each write.
O_CREAT If the file does not exist, it will be created.
O_LARGEFILE A file exceeding 2 GB can be created.
O_TRUNC If the file is opened successfully with O_WRONLY or O_RDWR, its length is truncated to 0.
O_EXCL Used together with O_CREAT. This function fails if the file exists.
O_DIRECTORY This flag must be added for opening a directory. Otherwise, the directory fails to be opened.

Attention:

This function can NOT be used in the PROC file system to create a file. This function is used to open a file. If the file does not exist, this function creates a file and opens it.

Returns:

Returns the file descriptor if the file is opened successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EACCES Search permission is denied on a component of the path prefix.
EINVAL The path name format is invalid.
ENAMETOOLONG The length of path is greater than the value of NAME_MAX.
ENOENT The O_CREAT flag is not set and the named file does not exist.
ENXIO Inode is invalid, not a normal character driver, or not a mount point.
EMFILE All available file descriptors of the process are opened.
EPERM The file structure corresponding to the file descriptor cannot be obtained.
EEXIST O_CREAT and O_EXCL are set.
EIO A hardware error occurs at the low-level disk I/O layer. As a result, the physical drive cannot work.
EROFS The named file resides on a read-only file system, and either O_WRONLY, O_RDWR, O_CREAT (if file does not exist), or O_TRUNC is set in the oflags parameter.
ENOSPC The directory or file system that would contain the new file cannot be expanded, the file does not exist, and O_CREAT is specified.
ENFILE The number of opened files in the system has reached the maximum.
EISDIR The named file is a directory, and oflags includes O_WRONLY, O_RDWR, or O_CREAT without O_DIRECTORY.
ENOTDIR A component of the path prefix names an existing file that is not a directory.
EBUSY The operation is rejected according to the file sharing policy.
ENODEV The device does not exist.
ENOTEMPTY The directory is not empty.
ELOOP Too many symbolic links are encountered.
EFAULT The IP address is incorrect.

opendir()


1. [DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849)* opendir (const char * dirname)

Description:

Opens a specified directory.

Parameters:

Name Description
dirname Indicates the pointer to the name of directory to open.

Returns:

Returns the pointer to the DIR structure representing the directory if it is opened successfully; returns NULL and sets errno to a value in the following table otherwise.

errno Description
EINVAL The dirname is empty.
ENAMETOOLONG The length of the path name string is longer than the value of NAME_MAX.
ENOENT The path component does not exist.
ENOMEM The storage memory is insufficient.
ENOTDIR dirname is not a directory.

readdir()


1. struct [dirent]($api-api-SmartVision-Devices-dirent.md)* readdir ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) * dirp)

Description:

Reads a specified directory.

Parameters:

Name Description
dirp Indicates the pointer to the directory structure.

Returns:

Returns the pointer to the dirent structure representing the directory if it is read successfully; returns NULL if reaching the end of the directory stream or the directory fails to be read. If the directory fails to be read, the corresponding error code is returned.

errno Description
EACCES This feature is not supported by the file system.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOENT The current position in the directory stream is invalid.
EBADF dirp is not an opened directory stream.

readdir_r()


1. int readdir_r ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) *__restrict dirp, struct [dirent]($api-api-SmartVision-Devices-dirent.md) *__restrict entry, struct [dirent]($api-api-SmartVision-Devices-dirent.md) **__restrict result )

Description:

Reads a specified directory (thread-safe version).

Parameters:

Name Description
dirp Indicates the pointer to the directory structure.
entry Indicates the entry read from the dirp stream.
result Indicates the pointer to the returned buffer.

Returns:

Returns 0. If the directory fails to be read, errno is sets to a value in the following table.

errno Description
EACCES This feature is not supported by the file system.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOENT The current position in the directory stream is invalid.
EBADF dirp is not an opened directory stream.

rewinddir()


1. void rewinddir ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) * dirp)

Description:

Resets a directory stream read position.

This function is used to change the current read position of the specified directory stream to the original read position (that is, the start position after the directory stream is opened by opendir).

Parameters:

Name Description
dirp Indicates the pointer to the directory stream whose read position needs to be reset.
errno Description
EBADF dirp is not an opened directory stream.

scandir()


1. int scandir (const char * dir, struct [dirent]($api-api-SmartVision-Devices-dirent.md) *** namelist, int(*)(const struct [dirent]($api-api-SmartVision-Devices-dirent.md) *) sel, int(*)(const struct [dirent]($api-api-SmartVision-Devices-dirent.md) **, const struct [dirent]($api-api-SmartVision-Devices-dirent.md) **) compar )

Description:

Scans directory to find the target entries.

Parameters:

Name Description
dir Indicates the pointer to the directory to scan.
namelist Indicates the array storing the directory entries filtered by the function referenced by the sel parameter.
sel Indicates the filtering condition. You can customize the function referenced by this parameter. Value 0 is returned if the filtering condition is not met; a non-zero value is returned otherwise.
compar Indicates the pointer to the function for sorting the directory entries.

Returns:

Returns the number of entries copied to the namelist array if the scanning is successful; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL dir is empty.
ENAMETOOLONG The length of the path name string is greater than the value of NAME_MAX.
ENOENT The directory component does not exist.
ENOMEM The storage memory is insufficient.
ENOTDIR dir is not a directory.
EACCES This feature is not supported by the file system.

seekdir()


1. void seekdir ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) * dirp, long offset )

Description:

Sets the position of the next readdir call in the directory stream.

Parameters:

Name Description
dirp Indicates the pointer to the directory stream in which the position of the next readdir call needs to be set.
offset Indicates the offset of the position relative to the current position.

stat()


1. int [stat]($api-api-SmartVision-Devices-stat.md) (const char *__restrict path, struct [stat]($api-api-SmartVision-Devices-stat.md) *__restrict buf )

Description:

Obtains file information.

Parameters:

Name Description
path Indicates the file path.
buf Indicates the pointer to a stat structure into which file information is placed.

Returns:

Returns 0 if file information is obtained successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL Invalid parameter.
ENOENT A component of path does not name an existing file or path is an empty string.
ENAMETOOLONG The path name length is greater than the value of NAME_MAX.
ENOMEM Insufficient memory.
ENOSYS The function is not supported.
EAGAIN The file list is null.
EACCES The permission bit of the file mode does not allow the requested access, or the search permission is denied on the path prefix component.
EEXIST The file or directory already exists.
EIO An I/O error occurs when data is read from or written to the file system.
EROFS The physical drive is write-protected.
ENOSPC No available space on the device.
ENFILE The number of opened files in the system has reached the maximum.
ENOTEMPTY The directory is not empty.
EISDIR The named file is a directory.
ENOTDIR A component of the path prefix is the name of an existing file. The file is neither a directory nor a symbolic link of a directory.
EPERM Operation not permitted or access denied because the access is prohibited or the directory is full.
EBUSY The operation is rejected according to the file sharing policy.
EPROTO The protocol in NFS is incorrect.
ENODEV No such device.
EFAULT Incorrect IP address.

statfs()


1. int statfs (const char * path, struct statfs * buf )

Description:

Obtains file system information of a file in a specified path.

Parameters:

Name Description
path Indicates the pointer to the name of the target file.
buf Indicates the pointer to a statfs structure that stores the information about the file system.

Returns:

Returns 0 if the operation is successful; returns -1 and sets errno to a value in the following table if the operation fails.

errno Description
EACCES Search permission is denied on a component of the path prefix.
EFAULT buf or path points to an invalid address.
EINTR The function call was interrupted by a signal.
EIO An I/O error occurred while reading from the file system.
ELOOP Too many symbolic links were found.
ENAMETOOLONG path is too long.
ENOENT The file referred to by path does not exist.
ENOMEM Insufficient memory.
ENOSYS The operation is not supported.
ENOTDIR A component of the path prefix of path is not a directory.
EOVERFLOW Information overflow

statvfs()


1. int [statvfs]($api-api-SmartVision-Devices-statvfs.md) (const char *__restrict path, struct [statvfs]($api-api-SmartVision-Devices-statvfs.md) *__restrict buf )

Description:

Obtains the file system information.

Parameters:

Name Description
path Indicates the pointer to the path name of the file.
buf Indicates the pointer to the statvfs structure that stores the obtained file system information.

Returns:

Returns 0 if the file system information is obtained successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EACCES Search permission is denied on a component of the path prefix.
EFAULT buf or path points to an invalid address.
EINTR This call was interrupted by a signal.
EIO An I/O error occurred while reading from the file system.
ELOOP Too many symbolic links were found.
ENAMETOOLONG path is too long.
ENOENT The file specified by path does not exist.
ENOMEM Insufficient memory.
ENOSYS The file system does not support this call.
ENOTDIR A component of the path prefix of path is not a directory.
EOVERFLOW Information overflows.

telldir()


1. long telldir ([DIR]($api-api-SmartVision-Devices-FS.md#ga0ebe68390948c14bb9d82987adbfc849) * dirp)

Description:

Obtains the current position in the specified directory stream.

Parameters:

Name Description
dirp Indicates the pointer to the directory stream.

Returns:

Returns the current position in the directory stream if the operation is successful; returns -1 and sets errno to the value in the following table otherwise.

errno Description
EBADF drip is not an opened directory stream.

umask()


1. mode_t umask (mode_t mode)

Description:

Sets umask for a process.

This function sets the umask of the current process file and returns the previous value of the umask. umask is used to turn off permission bits corresponding to in the mode parameter.

Parameters:

Name Description
mode Used to specify the umask value of a process.

Returns:

Returns the previous value of the umask. This function call always succeeds.

umount()


1. int umount (const char * target)

Description:

Unmounts a file system.

Parameters:

Name Description
target Indicates the pointer to the path of the file system to unmount.

Returns:

Returns 0 if the file system is unmounted successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EBUSY target could not be unmounted because it is busy.
EFAULT target points outside the user address space.
EINVAL target is not a mount point.
ENAMETOOLONG The path length is greater than the value of MAXPATHLEN.
ENOENT A path name is null or has a nonexistent component.
ENOMEM Insufficient memory.
EPERM No permission.

umount2()


1. int umount2 (const char * target, int flags )

Description:

Unmounts a file system.

This function is used to unmount a file system. Currently, the value of flags can only be 0. In this case, this function is the same as umount().

Parameters:

Name Description
target Indicates the pointer to the path of the file system to unmount.
flags Indicates the control flag. (Currently, the value of flags can only be 0. In this case, this function is the same as umount().)

Returns:

Returns 0 if the file system is unmounted successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EBUSY target could not be unmounted because it is busy.
EFAULT target points outside the user address space.
EINVAL target is not a mount point.
ENAMETOOLONG The path length is greater than the value of MAXPATHLEN.
ENOENT A path name is null or has a nonexistent component.
ENOMEM Insufficient memory.
EPERM No permission.
ENOSYS The function call is not supported. (flags value is not 0.)

utime()


1. int utime (const char * filename, const struct [utimbuf]($api-api-SmartVision-Devices-utimbuf.md) * times )

Description:

Sets the access time and modification time of a file.

Parameters:

Name Description
filename Indicates the pointer to the name of the file whose access time and modification time need to be set.
times Indicates the pointer to the time to which the access time and modification time are set. If times is a null pointer, then the access time and modification time are set to the current time.

Returns:

Returns 0 if the access time and modification time are set successfully; returns -1 and sets errno to a value in the following table otherwise.

errno Description
EINVAL filename is null or times is invalid.
ENAMETOOLONG The length of the component in the path name is greater than the value of NAME_MAX.
ENOENT Some paths do not exist.
ENOSYS This function is not supported.
EACCES The file system is read-only.
ENOMEM Insufficient memory.
EIO A hardware error occurs at the underlying disk I/O layer.