aboutsummaryrefslogtreecommitdiffstats
path: root/lib/ssh/doc/src/ssh_sftp.xml
blob: 95869befb81125aab2744417fe43860b2ba9aef3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2005</year><year>2014</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.

      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.

    </legalnotice>

    <title>ssh_sftp</title>
    <prepared>OTP</prepared>
    <docno></docno>
    <date>2005-09-22</date>
    <rev></rev>
    <file>ssh_sftp.sgml</file>
  </header>
  <module>ssh_sftp</module>
  <modulesummary>SFTP client.</modulesummary>
  <description>
    <p>This module implements an SSH FTP (SFTP) client. SFTP is a
    secure, encrypted file transfer service available for
    SSH.</p>
  </description>
  
 <section>
    <title>DATA TYPES</title>
    <p>Type definitions that are used more than once in this module,
    or abstractions to indicate the intended use of the data type, or both:
    </p>

    <taglist>
      <tag><c>ssh_connection_ref()</c></tag>
      <item><p>Opaque to the user, returned by <c>ssh:connect/3</c></p></item>
      <tag><c>timeout()</c></tag>
      <item><p>= <c>infinity | integer() in milliseconds</c></p></item>
    </taglist>
   </section>

 <section>
    <title>Time-outs</title>
    <p>If the request functions for the SFTP channel return <c>{error, timeout}</c>,
    it does not guarantee that the request never reached the server and was
    not performed. It only means that no answer was received from the
    server within the expected time.</p>
   </section>

  <funcs>
    <func>
      <name>start_channel(ConnectionRef) -></name>
      <name>start_channel(ConnectionRef, Options) -></name>
      <name>start_channel(Host, Options) -></name>
      <name>start_channel(Host, Port, Options) -> {ok, Pid} | {ok, Pid, ConnectionRef} |
      {error, Reason}</name>
      <fsummary>Starts an SFTP client.</fsummary>
      <type>
        <v>Host = string()</v>
        <v>ConnectionRef = ssh_connection_ref()</v>
        <v>Port = integer()</v>
        <v>Options = [{Option, Value}]</v>
        <v>Reason = term()</v>
      </type>
      <desc>
	<p>If no connection reference is provided, a connection is set
	up, and the new connection is returned. An SSH channel process
	is started to handle the communication with the SFTP server.
	The returned <c>pid</c> for this process is to be used as input to
	all other API functions in this module.</p>

	<p>Options:</p>
	<taglist>
          <tag><c><![CDATA[{timeout, timeout()}]]></c></tag>
	  <item>
	    <p>The time-out is passed to the <c>ssh_channel</c> start function,
	    and defaults to <c>infinity</c>.</p>
	  </item>
	  <tag>
	    <c><![CDATA[{sftp_vsn, integer()}]]></c>
	  </tag>
	  <item>
	    <p>
	      Desired SFTP protocol version.
	      The actual version is the minimum of
	      the desired version and the maximum supported
	      versions by the SFTP server.
	    </p>
	  </item>
	</taglist>
	<p>All other options are directly passed to
	<seealso marker="ssh">ssh:connect/3</seealso> or ignored if a
	connection is already provided.</p>
      </desc>
    </func>

    <func>
      <name>stop_channel(ChannelPid) -> ok</name>
      <fsummary>Stops the SFTP client channel.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
      </type>
      <desc>
	<p>Stops an SFTP channel. Does not close the SSH connection.
	Use <seealso marker="ssh">ssh:close/1</seealso> to close it.</p>
      </desc>
    </func>
  
    <func>
      <name>read_file(ChannelPid, File) -></name>
      <name>read_file(ChannelPid, File, Timeout) -> {ok, Data} | {error, Reason}</name>
      <fsummary>Reads a file.</fsummary>
      <type>
	<v>ChannelPid = pid()</v>
	<v>File = string()</v>
        <v>Data = binary()</v>
	<v>Timeout = timeout()</v>
	<v>Reason = term()</v>
      </type>
      <desc>
        <p>Reads a file from the server, and returns the data in a binary,
          like <c><![CDATA[file:read_file/1]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>write_file(ChannelPid, File, Iolist) -></name>
      <name>write_file(ChannelPid, File, Iolist, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Writes a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>File = string()</v>
        <v>Iolist = iolist()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Writes a file to the server, like
        <c><![CDATA[file:write_file/2]]></c>. The file is created if
        it does not exist. The file is overwritten if it exists.</p>
      </desc>
    </func>
    <func>
      <name>list_dir(ChannelPid, Path) -></name>
      <name>list_dir(ChannelPid, Path, Timeout) -> {ok, Filenames} | {error, Reason}</name>
      <fsummary>Lists the directory.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Path = string()</v>
        <v>Filenames = [Filename]</v>
        <v>Filename = string()</v>
	<v>Timeout = timeout()</v>
	<v>Reason = term()</v>
      </type>
      <desc>
        <p>Lists the given directory on the server, returning the
          filenames as a list of strings.</p>
      </desc>
    </func>
    <func>
      <name>open(ChannelPid, File, Mode) -></name>
      <name>open(ChannelPid, File, Mode, Timeout) -> {ok, Handle} | {error, Reason}</name>
      <fsummary>Opens a file and returns a handle.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>File = string()</v>
        <v>Mode = [Modeflag]</v>
        <v>Modeflag = read | write | creat | trunc | append | binary</v>
	<v>Timeout = timeout()</v>
	<v>Handle = term()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Opens a file on the server and returns a handle, which
          can be used for reading or writing.</p>
      </desc>
    </func>
    <func>
      <name>opendir(ChannelPid, Path) -></name>
      <name>opendir(ChannelPid, Path, Timeout) -> {ok, Handle} | {error, Reason}</name>
      <fsummary>Opens a directory and returns a handle.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Path = string()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Opens a handle to a directory on the server. The handle
          can be used for reading directory contents.</p>
      </desc>
    </func>

    <func>
      <name>open_tar(ChannelPid, Path, Mode) -></name>
      <name>open_tar(ChannelPid, Path, Mode, Timeout) -> {ok, Handle} | {error, Reason}</name>
      <fsummary>Opens a tar file on the server to which <c>ChannelPid</c>
      is connected and returns a handle.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Path = string()</v>
	<v>Mode = [read] | [write] | [read,EncryptOpt] | [write,DecryptOpt]</v>
	<v>EncryptOpt = {crypto,{InitFun,EncryptFun,CloseFun}}</v>
	<v>DecryptOpt = {crypto,{InitFun,DecryptFun}}</v>
	<v>InitFun = (fun() -> {ok,CryptoState}) | (fun() -> {ok,CryptoState,ChunkSize})</v>
	<v>CryptoState = any()</v>
	<v>ChunkSize = undefined | pos_integer()</v>
	<v>EncryptFun = (fun(PlainBin,CryptoState) -> EncryptResult)</v>
	<v>EncryptResult = {ok,EncryptedBin,CryptoState} | {ok,EncryptedBin,CryptoState,ChunkSize}</v>
	<v>PlainBin = binary()</v>
	<v>EncryptedBin = binary()</v>
	<v>DecryptFun = (fun(EncryptedBin,CryptoState) -> DecryptResult)</v>
	<v>DecryptResult = {ok,PlainBin,CryptoState} | {ok,PlainBin,CryptoState,ChunkSize}</v>
	<v>CloseFun = (fun(PlainBin,CryptoState) -> {ok,EncryptedBin})</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Opens a handle to a tar file on the server, associated with <c>ChannelPid</c>.
	The handle can be used for remote tar creation and extraction, as defined by the
	<seealso marker="stdlib:erl_tar#init/3">erl_tar:init/3</seealso> function.
	</p>
	<p>Example of writing and then reading a tar file follows:</p>
        <code type="none">
          {ok,HandleWrite} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [write]),
          ok = erl_tar:add(HandleWrite, .... ),
          ok = erl_tar:add(HandleWrite, .... ),
              ...
          ok = erl_tar:add(HandleWrite, .... ),
          ok = erl_tar:close(HandleWrite),

          %% And for reading
          {ok,HandleRead} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [read]),
          {ok,NameValueList} = erl_tar:extract(HandleRead,[memory]),
          ok = erl_tar:close(HandleRead),
        </code>

	<p>The <c>crypto</c> mode option is applied to the generated stream of bytes prior to sending
	them to the SFTP server. This is intended for encryption but can be used for other
	purposes.
	</p>
	<p>The <c>InitFun</c> is applied once
	prior to any other <c>crypto</c> operation. The returned <c>CryptoState</c> is then folded into
	repeated applications of the <c>EncryptFun</c> or <c>DecryptFun</c>. The binary returned
	from those funs are sent further to the remote SFTP server. Finally, if doing encryption,
	the <c>CloseFun</c> is applied to the last piece of data. The <c>CloseFun</c> is
	responsible for padding (if needed) and encryption of that last piece.
	</p>
	<p>The <c>ChunkSize</c> defines the size of the <c>PlainBin</c>s that <c>EncodeFun</c> is applied
	to. If the <c>ChunkSize</c> is <c>undefined</c>, the size of the <c>PlainBin</c>s varies,
	because this is	intended for stream crypto, whereas a fixed <c>ChunkSize</c> is intended for block crypto.
	<c>ChunkSize</c>s can be changed in the return from the <c>EncryptFun</c> or
	<c>DecryptFun</c>. The value can be changed between <c>pos_integer()</c> and <c>undefined</c>.
	</p>
	<p>The previous write and read example can be extended with encryption and decryption as follows:</p>
        <code type="none">
          %% First three parameters depending on which crypto type we select:
          Key = &lt;&lt;"This is a 256 bit key. abcdefghi">>,
          Ivec0 = crypto:rand_bytes(16),
          DataSize = 1024,  % DataSize rem 16 = 0 for aes_cbc

          %% Initialization of the CryptoState, in this case it is the Ivector.
          InitFun = fun() -> {ok, Ivec0, DataSize} end,

          %% How to encrypt:
          EncryptFun = 
              fun(PlainBin,Ivec) -> 
                   EncryptedBin = crypto:block_encrypt(aes_cbc256, Key, Ivec, PlainBin),
                   {ok, EncryptedBin, crypto:next_iv(aes_cbc,EncryptedBin)}
              end,

          %% What to do with the very last block:
          CloseFun = 
              fun(PlainBin, Ivec) ->
                    EncryptedBin = crypto:block_encrypt(aes_cbc256, Key, Ivec, 
                                                     pad(16,PlainBin) %% Last chunk
                                                     ),
                    {ok, EncryptedBin} 
            end,

          Cw = {InitFun,EncryptFun,CloseFun},
          {ok,HandleWrite} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [write,{crypto,Cw}]),
          ok = erl_tar:add(HandleWrite, .... ),
          ok = erl_tar:add(HandleWrite, .... ),
              ...
          ok = erl_tar:add(HandleWrite, .... ),
          ok = erl_tar:close(HandleWrite),

          %% And for decryption (in this crypto example we could use the same InitFun
          %% as for encryption):
          DecryptFun = 
              fun(EncryptedBin,Ivec) ->
                   PlainBin = crypto:block_decrypt(aes_cbc256, Key, Ivec, EncryptedBin),
                   {ok, PlainBin, crypto:next_iv(aes_cbc,EncryptedBin)}
              end,

          Cr = {InitFun,DecryptFun},
          {ok,HandleRead} = ssh_sftp:open_tar(ChannelPid, ?tar_file_name, [read,{crypto,Cw}]),
          {ok,NameValueList} = erl_tar:extract(HandleRead,[memory]),
          ok = erl_tar:close(HandleRead),
        </code>
      </desc>
    </func>

    <func>
      <name>close(ChannelPid, Handle) -></name>
      <name>close(ChannelPid, Handle, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Closes an open handle.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Closes a handle to an open file or directory on the server.</p>
      </desc>
    </func>
    <func>
      <name>read(ChannelPid, Handle, Len) -></name>
      <name>read(ChannelPid, Handle, Len, Timeout) -> {ok, Data} | eof | {error, Error}</name>
      <name>pread(ChannelPid, Handle, Position, Len) -></name>
      <name>pread(ChannelPid, Handle, Position, Len, Timeout) -> {ok, Data} | eof | {error, Error}</name>
      <fsummary>Reads from an open file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
        <v>Position = integer()</v>
        <v>Len = integer()</v>
	<v>Timeout = timeout()</v>
        <v>Data = string() | binary()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Reads <c><![CDATA[Len]]></c> bytes from the file referenced by
          <c><![CDATA[Handle]]></c>. Returns <c><![CDATA[{ok, Data}]]></c>, <c><![CDATA[eof]]></c>, or
          <c><![CDATA[{error, Reason}]]></c>. If the file is opened with <c><![CDATA[binary]]></c>,
          <c><![CDATA[Data]]></c> is a binary, otherwise it is a string.</p>
        <p>If the file is read past <c>eof</c>, only the remaining bytes
          are read and returned. If no bytes are read, <c><![CDATA[eof]]></c>
          is returned.</p>
        <p>The <c><![CDATA[pread]]></c> function reads from a specified position,
          combining the <c><![CDATA[position]]></c> and <c><![CDATA[read]]></c> functions.</p>
      </desc>
    </func>
    <func>
      <name>aread(ChannelPid, Handle, Len) -> {async, N} | {error, Error}</name>
      <name>apread(ChannelPid, Handle, Position, Len) -> {async, N} | {error, Error}</name>
      <fsummary>Reads asynchronously from an open file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
        <v>Position = integer()</v>
        <v>Len = integer()</v>
        <v>N = term()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Reads from an open file, without waiting for the result. If the
          handle is valid, the function returns <c><![CDATA[{async, N}]]></c>, where <c>N</c>
          is a term guaranteed to be unique between calls of <c><![CDATA[aread]]></c>. 
          The actual data is sent as a message to the calling process. This
          message has the form <c><![CDATA[{async_reply, N, Result}]]></c>, where
          <c><![CDATA[Result]]></c> is the result from the read, either <c><![CDATA[{ok, Data}]]></c>,
          <c><![CDATA[eof]]></c>, or <c><![CDATA[{error, Error}]]></c>.</p>
        <p>The <c><![CDATA[apread]]></c> function reads from a specified position,
          combining the <c><![CDATA[position]]></c> and <c><![CDATA[aread]]></c> functions.</p>
      </desc>
    </func>
    <func>
      <name>write(ChannelPid, Handle, Data) -></name>
      <name>write(ChannelPid, Handle, Data, Timeout) -> ok | {error, Error}</name>
      <name>pwrite(ChannelPid, Handle, Position, Data) -> ok</name>
      <name>pwrite(ChannelPid, Handle, Position, Data, Timeout) -> ok | {error, Error}</name>
      <fsummary>Writes to an open file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
        <v>Position = integer()</v>
        <v>Data = iolist()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Writes <c><![CDATA[data]]></c> to the file referenced by <c><![CDATA[Handle]]></c>.
          The file is to be opened with <c><![CDATA[write]]></c> or <c><![CDATA[append]]></c>
          flag. Returns <c><![CDATA[ok]]></c> if successful or <c><![CDATA[{error, Reason}]]></c>
          otherwise.</p>
        <p>Typical error reasons:</p>
        <taglist>
          <tag><c><![CDATA[ebadf]]></c></tag>
          <item>
            <p>File is not opened for writing.</p>
          </item>
          <tag><c><![CDATA[enospc]]></c></tag>
          <item>
            <p>No space is left on the device.</p>
          </item>
        </taglist>
      </desc>
    </func>
    <func>
      <name>awrite(ChannelPid, Handle, Data) -> ok | {error, Reason}</name>
      <name>apwrite(ChannelPid, Handle, Position, Data) -> ok | {error, Reason}</name>
      <fsummary>Writes asynchronously to an open file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
        <v>Position = integer()</v>
        <v>Len = integer()</v>
        <v>Data = binary()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Writes to an open file, without waiting for the result. If the
          handle is valid, the function returns <c><![CDATA[{async, N}]]></c>, where <c>N</c>
          is a term guaranteed to be unique between calls of
          <c><![CDATA[awrite]]></c>. The result of the <c><![CDATA[write]]></c> operation is sent
          as a message to the calling process. This message has the form
          <c><![CDATA[{async_reply, N, Result}]]></c>, where <c><![CDATA[Result]]></c> is the result
          from the write, either <c><![CDATA[ok]]></c>, or <c><![CDATA[{error, Error}]]></c>.</p>
        <p><c><![CDATA[apwrite]]></c> writes on a specified position, combining
          the <c><![CDATA[position]]></c> and <c><![CDATA[awrite]]></c> operations.</p>
      </desc>
    </func>
    <func>
      <name>position(ChannelPid, Handle, Location) -></name>
      <name>position(ChannelPid, Handle, Location, Timeout) -> {ok, NewPosition | {error, Error}</name>
      <fsummary>Sets the file position of a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Handle = term()</v>
        <v>Location = Offset
 | {bof, Offset} | {cur, Offset} | {eof, Offset} | bof | cur | eof</v>
        <v>Offset = integer()</v>
	<v>Timeout = timeout()</v>
        <v>NewPosition = integer()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Sets the file position of the file referenced by <c><![CDATA[Handle]]></c>.
          Returns <c><![CDATA[{ok, NewPosition}]]></c> (as an absolute offset) if
          successful, otherwise <c><![CDATA[{error, Reason}]]></c>. <c><![CDATA[Location]]></c> is
          one of the following:</p>
        <taglist>
          <tag><c><![CDATA[Offset]]></c></tag>
          <item>
            <p>The same as <c><![CDATA[{bof, Offset}]]></c>.</p>
          </item>
          <tag><c><![CDATA[{bof, Offset}]]></c></tag>
          <item>
            <p>Absolute offset.</p>
          </item>
          <tag><c><![CDATA[{cur, Offset}]]></c></tag>
          <item>
            <p>Offset from the current position.</p>
          </item>
          <tag><c><![CDATA[{eof, Offset}]]></c></tag>
          <item>
            <p>Offset from the end of file.</p>
          </item>
          <tag><c><![CDATA[bof | cur | eof]]></c></tag>
          <item>
            <p>The same as eariler with <c><![CDATA[Offset]]></c> 0,
	    that is, <c><![CDATA[{bof, 0} | {cur, 0} | {eof, 0}]]></c>.
	    </p>
          </item>
        </taglist>
      </desc>
    </func>
    <func>
      <name>read_file_info(ChannelPid, Name) -></name>
      <name>read_file_info(ChannelPid, Name, Timeout) -> {ok, FileInfo} | {error, Reason}</name>
      <fsummary>Gets information about a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
        <v>Handle = term()</v>
	<v>Timeout = timeout()</v>
        <v>FileInfo = record()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Returns a <c><![CDATA[file_info]]></c> record from the file specified by
          <c><![CDATA[Name]]></c> or <c><![CDATA[Handle]]></c>,
	like <c><![CDATA[file:read_file_info/2]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>read_link_info(ChannelPid, Name) -> {ok, FileInfo} | {error, Reason}</name>
      <name>read_link_info(ChannelPid, Name, Timeout) -> {ok, FileInfo} | {error, Reason}</name>
      <fsummary>Gets information about a symbolic link.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
        <v>Handle = term()</v>
	<v>Timeout = timeout()</v>
        <v>FileInfo = record()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Returns a <c><![CDATA[file_info]]></c> record from the symbolic
          link specified by <c><![CDATA[Name]]></c> or <c><![CDATA[Handle]]></c>, like
          <c><![CDATA[file:read_link_info/2]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>write_file_info(ChannelPid, Name, Info) -></name>
      <name>write_file_info(ChannelPid, Name, Info, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Writes information for a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
        <v>Info = record()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Writes file information from a <c><![CDATA[file_info]]></c> record to the
          file specified by <c><![CDATA[Name]]></c>, like <c><![CDATA[file:write_file_info]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>read_link(ChannelPid, Name) -></name>
      <name>read_link(ChannelPid, Name, Timeout) -> {ok, Target} | {error, Reason}</name>
      <fsummary>Reads symbolic link.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
        <v>Target = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Reads the link target from the symbolic link specified
          by <c><![CDATA[name]]></c>, like <c><![CDATA[file:read_link/1]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>make_symlink(ChannelPid, Name, Target) -></name>
      <name>make_symlink(ChannelPid, Name, Target, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Creates a symbolic link.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
        <v>Target = string()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Creates a symbolic link pointing to <c><![CDATA[Target]]></c> with the
          name <c><![CDATA[Name]]></c>, like <c><![CDATA[file:make_symlink/2]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>rename(ChannelPid, OldName, NewName) -> </name>
      <name>rename(ChannelPid, OldName, NewName, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Renames a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>OldName = string()</v>
        <v>NewName = string()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Renames a file named <c><![CDATA[OldName]]></c> and gives it the name
          <c><![CDATA[NewName]]></c>, like <c><![CDATA[file:rename/2]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>delete(ChannelPid, Name) -></name>
      <name>delete(ChannelPid, Name, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Deletes a file.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Deletes the file specified by <c><![CDATA[Name]]></c>, like
          <c><![CDATA[file:delete/1]]></c>.</p>
      </desc>
    </func>
    <func>
      <name>make_dir(ChannelPid, Name) -></name>
      <name>make_dir(ChannelPid, Name, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Creates a directory.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Creates a directory specified by <c><![CDATA[Name]]></c>. <c><![CDATA[Name]]></c>
          must be a full path to a new directory. The directory can only be
          created in an existing directory.</p>
      </desc>
    </func>
    <func>
      <name>del_dir(ChannelPid, Name) -></name>
      <name>del_dir(ChannelPid, Name, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Deletes an empty directory.</fsummary>
      <type>
        <v>ChannelPid = pid()</v>
        <v>Name = string()</v>
	<v>Timeout = timeout()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
	<p>Deletes a directory specified by <c><![CDATA[Name]]></c>.
	The directory must be empty before it can be successfully deleted.
	</p>
      </desc>
    </func>
  
  </funcs>
   
</erlref>