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1 | .\" Copyright (c) 1983, 1991 The Regents of the University of California. |
2 | .\" All rights reserved. | |
3 | .\" | |
a9cd9cb7 | 4 | .\" %%%LICENSE_START(BSD_4_CLAUSE_UCB) |
fea681da MK |
5 | .\" Redistribution and use in source and binary forms, with or without |
6 | .\" modification, are permitted provided that the following conditions | |
7 | .\" are met: | |
8 | .\" 1. Redistributions of source code must retain the above copyright | |
9 | .\" notice, this list of conditions and the following disclaimer. | |
10 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
11 | .\" notice, this list of conditions and the following disclaimer in the | |
12 | .\" documentation and/or other materials provided with the distribution. | |
13 | .\" 3. All advertising materials mentioning features or use of this software | |
14 | .\" must display the following acknowledgement: | |
15 | .\" This product includes software developed by the University of | |
16 | .\" California, Berkeley and its contributors. | |
17 | .\" 4. Neither the name of the University nor the names of its contributors | |
18 | .\" may be used to endorse or promote products derived from this software | |
19 | .\" without specific prior written permission. | |
20 | .\" | |
21 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
22 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
23 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
24 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
25 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
26 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
27 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
28 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
29 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
30 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
31 | .\" SUCH DAMAGE. | |
8c9302dc | 32 | .\" %%%LICENSE_END |
fea681da MK |
33 | .\" |
34 | .\" @(#)truncate.2 6.9 (Berkeley) 3/10/91 | |
35 | .\" | |
36 | .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu> | |
37 | .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com> | |
38 | .\" Modified 1998-12-21 by Andries Brouwer <aeb@cwi.nl> | |
c11b1abf | 39 | .\" Modified 2002-01-07 by Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 40 | .\" Modified 2002-04-06 by Andries Brouwer <aeb@cwi.nl> |
c11b1abf | 41 | .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 42 | .\" |
67d2c687 | 43 | .TH TRUNCATE 2 2015-05-07 "Linux" "Linux Programmer's Manual" |
fea681da MK |
44 | .SH NAME |
45 | truncate, ftruncate \- truncate a file to a specified length | |
46 | .SH SYNOPSIS | |
47 | .B #include <unistd.h> | |
48 | .br | |
49 | .B #include <sys/types.h> | |
50 | .sp | |
51 | .BI "int truncate(const char *" path ", off_t " length ); | |
52 | .br | |
53 | .BI "int ftruncate(int " fd ", off_t " length ); | |
cc4615cc MK |
54 | .sp |
55 | .in -4n | |
56 | Feature Test Macro Requirements for glibc (see | |
57 | .BR feature_test_macros (7)): | |
58 | .in | |
59 | .ad l | |
1e2ba090 | 60 | .PD 0 |
cc4615cc | 61 | .sp |
3ca7341f | 62 | .BR truncate (): |
729166ed | 63 | .RS 4 |
1e2ba090 MK |
64 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || |
65 | _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED | |
3ba63d80 MK |
66 | .br |
67 | || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L | |
729166ed | 68 | .RE |
1e2ba090 | 69 | .sp |
3ca7341f | 70 | .BR ftruncate (): |
729166ed | 71 | .RS 4 |
1e2ba090 | 72 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || |
1e2ba090 | 73 | _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED |
9dcef0c0 MK |
74 | .br |
75 | || /* Since glibc 2.3.5: */ _POSIX_C_SOURCE\ >=\ 200112L | |
729166ed | 76 | .RE |
1e2ba090 | 77 | .PD |
cc4615cc | 78 | .ad b |
fea681da MK |
79 | .SH DESCRIPTION |
80 | The | |
310b7919 | 81 | .BR truncate () |
fea681da | 82 | and |
310b7919 | 83 | .BR ftruncate () |
fea681da MK |
84 | functions cause the regular file named by |
85 | .I path | |
86 | or referenced by | |
87 | .I fd | |
88 | to be truncated to a size of precisely | |
89 | .I length | |
90 | bytes. | |
91 | .LP | |
c13182ef | 92 | If the file previously was larger than this size, the extra data is lost. |
fea681da | 93 | If the file previously was shorter, it is extended, and |
f81fb444 | 94 | the extended part reads as null bytes (\(aq\\0\(aq). |
fea681da | 95 | .LP |
1e568304 | 96 | The file offset is not changed. |
fea681da | 97 | .LP |
c13182ef | 98 | If the size changed, then the st_ctime and st_mtime fields |
310b7919 MK |
99 | (respectively, time of last status change and |
100 | time of last modification; see | |
101 | .BR stat (2)) | |
c13182ef | 102 | for the file are updated, |
ed948c28 | 103 | and the set-user-ID and set-group-ID mode bits may be cleared. |
fea681da MK |
104 | .LP |
105 | With | |
310b7919 | 106 | .BR ftruncate (), |
fea681da | 107 | the file must be open for writing; with |
310b7919 | 108 | .BR truncate (), |
fea681da | 109 | the file must be writable. |
47297adb | 110 | .SH RETURN VALUE |
c13182ef MK |
111 | On success, zero is returned. |
112 | On error, \-1 is returned, and | |
fea681da MK |
113 | .I errno |
114 | is set appropriately. | |
115 | .SH ERRORS | |
116 | For | |
e511ffb6 | 117 | .BR truncate (): |
fea681da MK |
118 | .TP |
119 | .B EACCES | |
120 | Search permission is denied for a component of the path prefix, | |
121 | or the named file is not writable by the user. | |
122 | (See also | |
ad7cc990 | 123 | .BR path_resolution (7).) |
fea681da MK |
124 | .TP |
125 | .B EFAULT | |
2d1b2fbc MK |
126 | The argument |
127 | .I path | |
fea681da MK |
128 | points outside the process's allocated address space. |
129 | .TP | |
130 | .B EFBIG | |
131 | The argument | |
132 | .I length | |
133 | is larger than the maximum file size. (XSI) | |
134 | .TP | |
135 | .B EINTR | |
374ce867 SL |
136 | While blocked waiting to complete, |
137 | the call was interrupted by a signal handler; see | |
138 | .BR fcntl (2) | |
139 | and | |
140 | .BR signal (7). | |
fea681da MK |
141 | .TP |
142 | .B EINVAL | |
143 | The argument | |
144 | .I length | |
145 | is negative or larger than the maximum file size. | |
146 | .TP | |
147 | .B EIO | |
148 | An I/O error occurred updating the inode. | |
149 | .TP | |
150 | .B EISDIR | |
151 | The named file is a directory. | |
152 | .TP | |
153 | .B ELOOP | |
154 | Too many symbolic links were encountered in translating the pathname. | |
155 | .TP | |
156 | .B ENAMETOOLONG | |
157 | A component of a pathname exceeded 255 characters, | |
2d7195b8 | 158 | or an entire pathname exceeded 1023 characters. |
fea681da MK |
159 | .TP |
160 | .B ENOENT | |
161 | The named file does not exist. | |
162 | .TP | |
163 | .B ENOTDIR | |
164 | A component of the path prefix is not a directory. | |
165 | .TP | |
5b548b31 | 166 | .B EPERM |
9ee4a2b6 | 167 | .\" This happens for at least MSDOS and VFAT filesystems |
5b548b31 | 168 | .\" on kernel 2.6.13 |
9ee4a2b6 | 169 | The underlying filesystem does not support extending |
5b548b31 MK |
170 | a file beyond its current size. |
171 | .TP | |
fbab10e5 MK |
172 | .B EPERM |
173 | The operation was prevented by a file seal; see | |
174 | .BR fcntl (2). | |
175 | .TP | |
fea681da | 176 | .B EROFS |
9ee4a2b6 | 177 | The named file resides on a read-only filesystem. |
fea681da MK |
178 | .TP |
179 | .B ETXTBSY | |
180 | The file is a pure procedure (shared text) file that is being executed. | |
181 | .PP | |
182 | For | |
310b7919 | 183 | .BR ftruncate () |
fea681da MK |
184 | the same errors apply, but instead of things that can be wrong with |
185 | .IR path , | |
3ade1aa9 | 186 | we now have things that can be wrong with the file descriptor, |
fea681da MK |
187 | .IR fd : |
188 | .TP | |
189 | .B EBADF | |
fea681da MK |
190 | .I fd |
191 | is not a valid descriptor. | |
192 | .TP | |
193 | .BR EBADF " or " EINVAL | |
fea681da MK |
194 | .I fd |
195 | is not open for writing. | |
196 | .TP | |
197 | .B EINVAL | |
fea681da MK |
198 | .I fd |
199 | does not reference a regular file. | |
47297adb | 200 | .SH CONFORMING TO |
97c1eac8 MK |
201 | 4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD). |
202 | .\" POSIX.1-1996 has | |
203 | .\" .BR ftruncate (). | |
204 | .\" POSIX.1-2001 also has | |
205 | .\" .BR truncate (), | |
206 | .\" as an XSI extension. | |
207 | .\" .LP | |
208 | .\" SVr4 documents additional | |
209 | .\" .BR truncate () | |
210 | .\" error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK. SVr4 documents for | |
211 | .\" .BR ftruncate () | |
212 | .\" an additional EAGAIN error condition. | |
fea681da | 213 | .SH NOTES |
c0697399 | 214 | The details in DESCRIPTION are for XSI-compliant systems. |
fea681da | 215 | For non-XSI-compliant systems, the POSIX standard allows |
d9bfdb9c | 216 | two behaviors for |
310b7919 | 217 | .BR ftruncate () |
fea681da MK |
218 | when |
219 | .I length | |
220 | exceeds the file length | |
221 | (note that | |
310b7919 | 222 | .BR truncate () |
fea681da MK |
223 | is not specified at all in such an environment): |
224 | either returning an error, or extending the file. | |
008f1ecc | 225 | Like most UNIX implementations, Linux follows the XSI requirement |
9ee4a2b6 MK |
226 | when dealing with native filesystems. |
227 | However, some nonnative filesystems do not permit | |
5b548b31 | 228 | .BR truncate () |
c13182ef | 229 | and |
5b548b31 MK |
230 | .BR ftruncate () |
231 | to be used to extend a file beyond its current length: | |
232 | a notable example on Linux is VFAT. | |
fea681da | 233 | .\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002 |
0290f437 MK |
234 | |
235 | The original Linux | |
236 | .BR truncate () | |
237 | and | |
238 | .BR ftruncate () | |
239 | system calls were not designed to handle large file offsets. | |
240 | Consequently, Linux 2.4 added | |
241 | .BR truncate64 () | |
242 | and | |
243 | .BR ftruncate64 () | |
244 | system calls that handle large files. | |
245 | However, these details can be ignored by applications using glibc, whose | |
dd7f1928 | 246 | wrapper functions transparently employ the more recent system calls |
0290f437 | 247 | where they are available. |
63ec43ae MK |
248 | |
249 | On some 32-bit architectures, | |
250 | the calling signature for these system calls differ, | |
251 | for the reasons described in | |
252 | .BR syscall (2). | |
9dcef0c0 MK |
253 | .SH BUGS |
254 | A header file bug in glibc 2.12 meant that the minimum value of | |
255 | .\" http://sourceware.org/bugzilla/show_bug.cgi?id=12037 | |
256 | .BR _POSIX_C_SOURCE | |
257 | required to expose the declaration of | |
258 | .BR ftruncate () | |
259 | was 200809L instead of 200112L. | |
260 | This has been fixed in later glibc versions. | |
47297adb | 261 | .SH SEE ALSO |
fea681da | 262 | .BR open (2), |
ad7cc990 MK |
263 | .BR stat (2), |
264 | .BR path_resolution (7) |