file

Changes group of a file. See write_file_info/2.

更改文件的所属组. 参阅 write_file_info/2.

Changes permissions of a file. See write_file_info/2.

更改文件权限. 参阅 write_file_info/2.

Changes owner of a file. See write_file_info/2.

更改文件的所有者. 参阅 write_file_info/2.

Changes owner and group of a file. See write_file_info/2.

更改文件的所有者和所有组. 参阅 write_file_info/2.

Changes the modification and access times of a file. See write_file_info/2.

更改文件的修改和访问时间. 参阅 write_file_info/2.

Changes the modification and last access times of a file. See write_file_info/2.

更改文件的修改和访问时间. 参阅 write_file_info/2.

Closes the file referenced by IoDevice. It mostly returns ok, expect for some severe errors such as out of memory.

关闭IoDevice引用的文件. 这通常会返回ok, 除非发生像超出内存这样的服务器错误.

Note that if the option delayed_write was used when opening the file, close/1 might return an old write error and not even try to close the file. See open/2.

注意，如果在打开文件的时候使用了delayed_write 选项, close/1 可能返回一个过时写错误，甚至不会尝试关闭这个文件. 参阅 open/2.

Reads Erlang terms, separated by '.', from Filename. Returns one of the following:

从Filename中读取用'.'分隔的Erlang项. 返回下列其中一种:

Example:

示例:

f.txt:  {person, "kalle", 25}.
        {person, "pelle", 30}.

1> file:consult("f.txt").
{ok,[{person,"kalle",25},{person,"pelle",30}]}

Copies ByteCount bytes from Source to Destination. Source and Destination refer to either filenames or IO devices from e.g. open/2. ByteCount defaults to infinity, denoting an infinite number of bytes.

从Source 向 Destination拷贝ByteCount字节. Source 和 Destination 指向文件名或IO设备(例如open/2返回的IO). ByteCount 默认值 infinity, 代表无限字节.

The argument Modes is a list of possible modes, see open/2, and defaults to [].

参数Modes 是一个模式列表, 参阅 open/2, 默认值为[].

If both Source and Destination refer to filenames, the files are opened with [read, binary] and [write, binary] prepended to their mode lists, respectively, to optimize the copy.

如果Source 和 Destination 都是文件名, 那么这些文件将会分别以[read, binary] 和[write, binary] 作为模式列表的前缀来优化拷贝.

If Source refers to a filename, it is opened with read mode prepended to the mode list before the copy, and closed when done.

如果 Source 是一个文件名, 那么它会在拷贝之前以read作为模式列表的前缀打开, 并且在结束的时候关闭.

If Destination refers to a filename, it is opened with write mode prepended to the mode list before the copy, and closed when done.

如果 Destination 是一个文件名, 那么它会在拷贝之前以write作为模式列表的前缀打开, 并且在结束的时候关闭.

Returns {ok, BytesCopied} where BytesCopied is the number of bytes that actually was copied, which may be less than ByteCount if end of file was encountered on the source. If the operation fails, {error, Reason} is returned.

返回 {ok, BytesCopied} 其中BytesCopied 是实际拷贝的字节数，如果遇到了文件结束符可能会小于ByteCount. 如果操作失败返回 {error, Reason}.

Typical error reasons: As for open/2 if a file had to be opened, and as for read/2 and write/2.

典型的错误原因: 如果需要打开文件时参阅open/2 , 以及read/2 和write/2.

Tries to delete the directory Dir. The directory must be empty before it can be deleted. Returns ok if successful.

尝试删除文件夹Dir.删除之前文件夹必须为空. 如果删除成功返回ok.

Typical error reasons are:

典型的错误原因:

Tries to delete the file Filename. Returns ok if successful.

尝试删除文件Filename.如果成功, 返回ok.

Typical error reasons are:

典型的错误原因:

Reads and evaluates Erlang expressions, separated by '.' (or ',', a sequence of expressions is also an expression), from Filename. The actual result of the evaluation is not returned; any expression sequence in the file must be there for its side effect. Returns one of the following:

从Filename读取并且计算Erlang表达式, separated by '.' (or ',', a sequence of expressions is also an expression), from . 实际的计算结果并不返回; 并且任何any expression sequence in the file must be there for its side effect. 返回下列之一:

The same as eval/1 but the variable bindings Bindings are used in the evaluation. See erl_eval(3) about variable bindings.

除了在计算过程中使用变量绑定Bindings 以外与eval/1相同. 参阅 erl_eval(3) 中关于变量绑定的内容.

This function is obsolete. Use read_file_info/1,2 instead.

该函数已过时. 请使用read_file_info/1,2.

Given the error reason returned by any function in this module, returns a descriptive string of the error in English.

给定一个由本模块任何一个函数返回的错误原因, 返回该错误的英文描述字符串.

Returns {ok, Dir}, where Dir is the current working directory of the file server.

返回 {ok, Dir}, 其中 Dir是文件服务器的当前工作目录.

Typical error reasons are:

典型的错误原因:

Drive should be of the form "Letter:", for example "c:". Returns {ok, Dir} or {error, Reason}, where Dir is the current working directory of the drive specified.

Drive 应该是"Letter:"的形式, 例如"c:". 返回 {ok, Dir} 或 {error, Reason}, 其中 Dir 是指定分区上的当前工作目录.

This function returns {error, enotsup} on platforms which have no concept of current drive (Unix, for example).

该函数在没有当前分区概念的平台(例如Unix)上返回{error, enotsup}.

Typical error reasons are:

典型的错误原因:

Lists all the files in a directory. Returns {ok, Filenames} if successful. Otherwise, it returns {error, Reason}. Filenames is a list of the names of all the files in the directory. The names are not sorted.

列出文件夹下的所有文件. 如果成功, 返回{ok, Filenames}. 否则, 返回{error, Reason}. Filenames 是一个包含文件夹中所有文件名的列表. 这些名字没有排序.

Typical error reasons are:

典型的错误原因:

Tries to create the directory Dir. Missing parent directories are not created. Returns ok if successful.

尝试创建文件夹Dir. 缺失父文件夹时不创建文件夹. 如果成功, 返回ok.

Typical error reasons are:

典型的错误原因:

Makes a hard link from Existing to New, on platforms that support links (Unix and Windows). This function returns ok if the link was successfully created, or {error, Reason}. On platforms that do not support links, {error,enotsup} is returned.

在支持链接的平台上（例如unix, windows)创建一个从Existing到New的硬链接. 如果链接创建成功返回 ok, 否则返回 {error, Reason}. 在不支持链接的平台上, 返回{error,enotsup} .

Typical error reasons:

典型的错误原因:

This function creates a symbolic link New to the file or directory Existing, on platforms that support symbolic links (most Unix systems and Windows beginning with Vista). Existing need not exist. This function returns ok if the link was successfully created, or {error, Reason}. On platforms that do not support symbolic links, {error, enotsup} is returned.

在支持符号链接的平台上（例如unix, Vista之后的windows)创建一个从Existing到New的符号链接. Existing不必一定存在. 如果创建成功返回 ok, 否则返回 {error, Reason}. 在不支持符号链接的平台上, 返回{error,enotsup} .

Typical error reasons:

典型的错误原因:

This function returns the configured default file name encoding to use for raw file names. Generally an application supplying file names raw (as binaries), should obey the character encoding returned by this function.

By default, the VM uses ISO-latin-1 file name encoding on filesystems and/or OSes that use completely transparent file naming. This includes all Unix versions except MacOSX, where the vfs layer enforces UTF-8 file naming. By giving the experimental option +fnu when starting Erlang, UTF-8 translation of file names can be turned on even for those systems. If Unicode file name translation is in effect, the system behaves as usual as long as file names conform to the encoding, but will return file names that are not properly encoded in UTF-8 as raw file names (i.e. binaries).

On Windows, this function also returns utf8 by default. The OS uses a pure Unicode naming scheme and file names are always possible to interpret as valid Unicode. The fact that the underlying Windows OS actually encodes file names using little endian UTF-16 can be ignored by the Erlang programmer. Windows and MacOSX are the only operating systems where the VM operates in Unicode file name mode by default.

Opens the file Filename in the mode determined by Modes, which may contain one or more of the following items:

以由Modes确定的模式打开文件Filename, 这些模式可以包含下述一个或多个项:

Returns:

返回值:

IoDevice is really the pid of the process which handles the file. This process is linked to the process which originally opened the file. If any process to which the IoDevice is linked terminates, the file will be closed and the process itself will be terminated. An IoDevice returned from this call can be used as an argument to the IO functions (see io(3)).

IoDevice 是处理文件的进程号. 该进程与最初打开文件的进程相链接. 如果IoDevice链接的任意一个进程终止，那么文件将被关闭而该进程也会被终止. 由该函数调用返回的 IoDevice 可以作为IO函数的参数(参阅 io(3)).

Typical error reasons:

典型的错误原因:

Searches the path Path (a list of directory names) until the file Filename is found. If Filename is an absolute filename, Path is ignored. Then reads Erlang terms, separated by '.', from the file. Returns one of the following:

搜索路径Path (一个文件夹路径列表) 直到发现Filename文件. 如果Filename是一个绝对路径, 那么将会忽略Path. 之后从文件中读取以'.'分隔的Erlang项. 返回下列之一:

Searches the path Path (a list of directory names) until the file Filename is found. If Filename is an absolute file name, Path is ignored. Then reads and evaluates Erlang expressions, separated by '.' (or ',', a sequence of expressions is also an expression), from the file. The actual result of evaluation is not returned; any expression sequence in the file must be there for its side effect. Returns one of the following:

搜索路径Path (一个文件夹路径列表) 直到发现Filename文件. 如果Filename是一个绝对路径, 那么将会忽略Path. Then reads and evaluates Erlang expressions, separated by '.' (or ',', a sequence of expressions is also an expression), from the file. The actual result of evaluation is not returned; any expression sequence in the file must be there for its side effect. Returns one of the following:

Searches the path Path (a list of directory names) until the file Filename is found. If Filename is an absolute file name, Path is ignored. Then opens the file in the mode determined by Modes. Returns one of the following:

搜索路径Path (一个文件夹路径列表) 直到发现Filename文件. 如果Filename是一个绝对路径, 那么将会忽略Path. 之后以Modes确定的模式打开文件. 返回下列之一:

Searches the path Path (a list of directory names) until the file Filename is found. If Filename is an absolute file name, Path is ignored. Then reads and evaluates Erlang expressions, separated by '.' (or ',', a sequence of expressions is also an expression), from the file. Returns one of the following:

The same as path_script/2 but the variable bindings Bindings are used in the evaluation. See erl_eval(3) about variable bindings.

If Pid is an IO device, that is, a pid returned from open/2, this function returns the filename, or rather:

如果Pid 是一个IO设备, 也就是说该进程号是由open/2返回的, 该函数返回相应的文件名, 更确切的是:

Sets the position of the file referenced by IoDevice to Location. Returns {ok, NewPosition} (as absolute offset) if successful, otherwise {error, Reason}. Location is one of the following:

设置IoDevice引用的文件指针位置为Location. 如果成功的话返回{ok, NewPosition} (绝对文件偏移量), 否则返回{error, Reason}. Location为下列之一:

Note that offsets are counted in bytes, not in characters. If the file is opened using some other encoding than latin1, one byte does not correspond to one character. Positioning in such a file can only be done to known character boundaries, i.e. to a position earlier retrieved by getting a current position, to the beginning/end of the file or to some other position known to be on a correct character boundary by some other means (typically beyond a byte order mark in the file, which has a known byte-size).

注意, 偏移量的单位是字节而不是字符. 如果文件以其他的encoding 而不是latin1打开时, 一个字节并不对应一个字符. Positioning in such a file can only be done to known character boundaries, i.e. to a position earlier retrieved by getting a current position, to the beginning/end of the file or to some other position known to be on a correct character boundary by some other means (typically beyond a byte order mark in the file, which has a known byte-size).

Typical error reasons are:

典型的错误原因:

Performs a sequence of pread/3 in one operation, which is more efficient than calling them one at a time. Returns {ok, [Data, ...]} or {error, Reason}, where each Data, the result of the corresponding pread, is either a list or a binary depending on the mode of the file, or eof if the requested position was beyond end of file.

As the position is given as a byte-offset, special caution has to be taken when working with files where encoding is set to something else than latin1, as not every byte position will be a valid character boundary on such a file.

Combines position/2 and read/2 in one operation, which is more efficient than calling them one at a time. If IoDevice has been opened in raw mode, some restrictions apply: Location is only allowed to be an integer; and the current position of the file is undefined after the operation.

As the position is given as a byte-offset, special caution has to be taken when working with files where encoding is set to something else than latin1, as not every byte position will be a valid character boundary on such a file.

Performs a sequence of pwrite/3 in one operation, which is more efficient than calling them one at a time. Returns ok or {error, {N, Reason}}, where N is the number of successful writes that was done before the failure.

When positioning in a file with other encoding than latin1, caution must be taken to set the position on a correct character boundary, see position/2 for details.

Combines position/2 and write/2 in one operation, which is more efficient than calling them one at a time. If IoDevice has been opened in raw mode, some restrictions apply: Location is only allowed to be an integer; and the current position of the file is undefined after the operation.

When positioning in a file with other encoding than latin1, caution must be taken to set the position on a correct character boundary, see position/2 for details.

Reads Number bytes/characters from the file referenced by IoDevice. The functions read/2, pread/3 and read_line/1 are the only ways to read from a file opened in raw mode (although they work for normally opened files, too).

For files where encoding is set to something else than latin1, one character might be represented by more than one byte on the file. The parameter Number always denotes the number of characters read from the file, why the position in the file might be moved a lot more than this number when reading a Unicode file.

Also if encoding is set to something else than latin1, the read/3 call will fail if the data contains characters larger than 255, why the io(3) module is to be preferred when reading such a file.

The function returns:

Typical error reasons:

典型的错误原因:

Returns {ok, Binary}, where Binary is a binary data object that contains the contents of Filename, or {error, Reason} if an error occurs.

Typical error reasons:

典型的错误原因:

Retrieves information about a file. Returns {ok, FileInfo} if successful, otherwise {error, Reason}. FileInfo is a record file_info, defined in the Kernel include file file.hrl. Include the following directive in the module from which the function is called:

-include_lib("kernel/include/file.hrl").

The time type returned in atime, mtime and ctime is dependent on the time type set in Opts :: {time, Type}. Type local will return local time, universal will return universal time and posix will return seconds since or before unix time epoch which is 1970-01-01 00:00 UTC. Default is {time, local}.

The record file_info contains the following fields.

Typical error reasons:

典型的错误原因:

Reads a line of bytes/characters from the file referenced by IoDevice. Lines are defined to be delimited by the linefeed (LF, \n) character, but any carriage return (CR, \r) followed by a newline is also treated as a single LF character (the carriage return is silently ignored). The line is returned including the LF, but excluding any CR immediately followed by a LF. This behaviour is consistent with the behaviour of io:get_line/2. If end of file is reached without any LF ending the last line, a line with no trailing LF is returned.

The function can be used on files opened in raw mode. It is however inefficient to use it on raw files if the file is not opened with the option {read_ahead, Size} specified, why combining raw and {read_ahead, Size} is highly recommended when opening a text file for raw line oriented reading.

If encoding is set to something else than latin1, the read_line/1 call will fail if the data contains characters larger than 255, why the io(3) module is to be preferred when reading such a file.

The function returns:

Typical error reasons:

典型的错误原因:

This function returns {ok, Filename} if Name refers to a symbolic link or {error, Reason} otherwise. On platforms that do not support symbolic links, the return value will be {error,enotsup}.

Typical error reasons:

典型的错误原因:

This function works like read_file_info/1,2 except that if Name is a symbolic link, information about the link will be returned in the file_info record and the type field of the record will be set to symlink.

If Name is not a symbolic link, this function returns exactly the same result as read_file_info/1. On platforms that do not support symbolic links, this function is always equivalent to read_file_info/1.

Tries to rename the file Source to Destination. It can be used to move files (and directories) between directories, but it is not sufficient to specify the destination only. The destination file name must also be specified. For example, if bar is a normal file and foo and baz are directories, rename("foo/bar", "baz") returns an error, but rename("foo/bar", "baz/bar") succeeds. Returns ok if it is successful.

Typical error reasons:

典型的错误原因:

Reads and evaluates Erlang expressions, separated by '.' (or ',', a sequence of expressions is also an expression), from the file. Returns one of the following:

The same as script/1 but the variable bindings Bindings are used in the evaluation. See erl_eval(3) about variable bindings.

Sets the current working directory of the file server to Dir. Returns ok if successful.

Typical error reasons are:

典型的错误原因:

Makes sure that any buffers kept by the operating system (not by the Erlang runtime system) are written to disk. On some platforms, this function might have no effect.

Typical error reasons are:

典型的错误原因:

Makes sure that any buffers kept by the operating system (not by the Erlang runtime system) are written to disk. In many ways it's resembles fsync but it not requires to update some of file's metadata such as the access time. On some platforms, this function might have no effect.

Applications that access databases or log files often write a tiny data fragment (e.g., one line in a log file) and then call fsync() immediately in order to ensure that the written data is physically stored on the harddisk. Unfortunately, fsync() will always initiate two write operations: one for the newly written data and another one in order to update the modification time stored in the inode. If the modification time is not a part of the transaction concept fdatasync() can be used to avoid unnecessary inode disk write operations.

Available only in some POSIX systems. This call results in a call to fsync(), or has no effect, in systems not implementing the fdatasync syscall.

Truncates the file referenced by IoDevice at the current position. Returns ok if successful, otherwise {error, Reason}.

Sends the file Filename to Socket. Returns {ok, BytesSent} if successful, otherwise {error, Reason}.

Sends Bytes from the file referenced by RawFile beginning at Offset to Socket. Returns {ok, BytesSent} if successful, otherwise {error, Reason}. If Bytes is set to 0 all data after the given Offset is sent.

The file used must be opened using the raw flag, and the process calling sendfile must be the controlling process of the socket. See gen_tcp:controlling_process/2

If the OS used does not support sendfile, an Erlang fallback using file:read and gen_tcp:send is used.

The option list can contain the following options:

On operating systems with thread support, it is recommended to use async threads. See the command line flag +A in erl(1). If it is not possible to use async threads for sendfile, it is recommended to use a relatively small value for the send buffer on the socket. Otherwise the Erlang VM might loose some of its soft realtime guarantees. Which size to use depends on the OS/hardware and the requirements of the application.

Writes Bytes to the file referenced by IoDevice. This function is the only way to write to a file opened in raw mode (although it works for normally opened files, too). Returns ok if successful, and {error, Reason} otherwise.

If the file is opened with encoding set to something else than latin1, each byte written might result in several bytes actually being written to the file, as the byte range 0..255 might represent anything between one and four bytes depending on value and UTF encoding type.

Typical error reasons are:

典型的错误原因:

Writes the contents of the iodata term Bytes to the file Filename. The file is created if it does not exist. If it exists, the previous contents are overwritten. Returns ok, or {error, Reason}.

Typical error reasons are:

典型的错误原因:

Same as write_file/2, but takes a third argument Modes, a list of possible modes, see open/2. The mode flags binary and write are implicit, so they should not be used.

Change file information. Returns ok if successful, otherwise {error, Reason}. FileInfo is a record file_info, defined in the Kernel include file file.hrl. Include the following directive in the module from which the function is called:

-include_lib("kernel/include/file.hrl").

The time type set in atime, mtime and ctime is dependent on the time type set in Opts :: {time, Type}. Type local will interpret the time set as local, universal will interpret it as universal time and posix must be seconds since or before unix time epoch which is 1970-01-01 00:00 UTC. Default is {time, local}.

The following fields are used from the record, if they are given.

Typical error reasons:

典型的错误原因: