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1 | .\" Copyright (c) 1983, 1991 The Regents of the University of California. |
2 | .\" All rights reserved. | |
3 | .\" | |
4 | .\" Redistribution and use in source and binary forms, with or without | |
5 | .\" modification, are permitted provided that the following conditions | |
6 | .\" are met: | |
7 | .\" 1. Redistributions of source code must retain the above copyright | |
8 | .\" notice, this list of conditions and the following disclaimer. | |
9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer in the | |
11 | .\" documentation and/or other materials provided with the distribution. | |
12 | .\" 3. All advertising materials mentioning features or use of this software | |
13 | .\" must display the following acknowledgement: | |
14 | .\" This product includes software developed by the University of | |
15 | .\" California, Berkeley and its contributors. | |
16 | .\" 4. Neither the name of the University nor the names of its contributors | |
17 | .\" may be used to endorse or promote products derived from this software | |
18 | .\" without specific prior written permission. | |
19 | .\" | |
20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
30 | .\" SUCH DAMAGE. | |
31 | .\" | |
32 | .\" @(#)truncate.2 6.9 (Berkeley) 3/10/91 | |
33 | .\" | |
34 | .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu> | |
35 | .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com> | |
36 | .\" Modified 1998-12-21 by Andries Brouwer <aeb@cwi.nl> | |
c11b1abf | 37 | .\" Modified 2002-01-07 by Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 38 | .\" Modified 2002-04-06 by Andries Brouwer <aeb@cwi.nl> |
c11b1abf | 39 | .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com> |
fea681da | 40 | .\" |
3ade1aa9 | 41 | .TH TRUNCATE 2 2008-07-04 "Linux" "Linux Programmer's Manual" |
fea681da MK |
42 | .SH NAME |
43 | truncate, ftruncate \- truncate a file to a specified length | |
44 | .SH SYNOPSIS | |
45 | .B #include <unistd.h> | |
46 | .br | |
47 | .B #include <sys/types.h> | |
48 | .sp | |
49 | .BI "int truncate(const char *" path ", off_t " length ); | |
50 | .br | |
51 | .BI "int ftruncate(int " fd ", off_t " length ); | |
cc4615cc MK |
52 | .sp |
53 | .in -4n | |
54 | Feature Test Macro Requirements for glibc (see | |
55 | .BR feature_test_macros (7)): | |
56 | .in | |
57 | .ad l | |
58 | .sp | |
59 | .BR getdtablesize (): | |
60 | _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 || _POSIX_C_SOURCE\ >=\ 200112L | |
61 | .ad b | |
fea681da MK |
62 | .SH DESCRIPTION |
63 | The | |
310b7919 | 64 | .BR truncate () |
fea681da | 65 | and |
310b7919 | 66 | .BR ftruncate () |
fea681da MK |
67 | functions cause the regular file named by |
68 | .I path | |
69 | or referenced by | |
70 | .I fd | |
71 | to be truncated to a size of precisely | |
72 | .I length | |
73 | bytes. | |
74 | .LP | |
c13182ef | 75 | If the file previously was larger than this size, the extra data is lost. |
fea681da | 76 | If the file previously was shorter, it is extended, and |
f81fb444 | 77 | the extended part reads as null bytes (\(aq\\0\(aq). |
fea681da | 78 | .LP |
1e568304 | 79 | The file offset is not changed. |
fea681da | 80 | .LP |
c13182ef | 81 | If the size changed, then the st_ctime and st_mtime fields |
310b7919 MK |
82 | (respectively, time of last status change and |
83 | time of last modification; see | |
84 | .BR stat (2)) | |
c13182ef | 85 | for the file are updated, |
310b7919 | 86 | and the set-user-ID and set-group-ID permission bits may be cleared. |
fea681da MK |
87 | .LP |
88 | With | |
310b7919 | 89 | .BR ftruncate (), |
fea681da | 90 | the file must be open for writing; with |
310b7919 | 91 | .BR truncate (), |
fea681da MK |
92 | the file must be writable. |
93 | .SH "RETURN VALUE" | |
c13182ef MK |
94 | On success, zero is returned. |
95 | On error, \-1 is returned, and | |
fea681da MK |
96 | .I errno |
97 | is set appropriately. | |
98 | .SH ERRORS | |
99 | For | |
e511ffb6 | 100 | .BR truncate (): |
fea681da MK |
101 | .TP |
102 | .B EACCES | |
103 | Search permission is denied for a component of the path prefix, | |
104 | or the named file is not writable by the user. | |
105 | (See also | |
ad7cc990 | 106 | .BR path_resolution (7).) |
fea681da MK |
107 | .TP |
108 | .B EFAULT | |
109 | .I Path | |
110 | points outside the process's allocated address space. | |
111 | .TP | |
112 | .B EFBIG | |
113 | The argument | |
114 | .I length | |
115 | is larger than the maximum file size. (XSI) | |
116 | .TP | |
117 | .B EINTR | |
118 | A signal was caught during execution. | |
119 | .TP | |
120 | .B EINVAL | |
121 | The argument | |
122 | .I length | |
123 | is negative or larger than the maximum file size. | |
124 | .TP | |
125 | .B EIO | |
126 | An I/O error occurred updating the inode. | |
127 | .TP | |
3ade1aa9 MK |
128 | .B EINTR |
129 | While blocked waiting to complete, | |
130 | the call was interrupted by a signal handler; see | |
131 | .BR fcntl (2) | |
132 | and | |
133 | .BR signal (7). | |
134 | .TP | |
fea681da MK |
135 | .B EISDIR |
136 | The named file is a directory. | |
137 | .TP | |
138 | .B ELOOP | |
139 | Too many symbolic links were encountered in translating the pathname. | |
140 | .TP | |
141 | .B ENAMETOOLONG | |
142 | A component of a pathname exceeded 255 characters, | |
2d7195b8 | 143 | or an entire pathname exceeded 1023 characters. |
fea681da MK |
144 | .TP |
145 | .B ENOENT | |
146 | The named file does not exist. | |
147 | .TP | |
148 | .B ENOTDIR | |
149 | A component of the path prefix is not a directory. | |
150 | .TP | |
5b548b31 MK |
151 | .B EPERM |
152 | .\" This happens for at leas MSDOS and VFAT fil systems | |
153 | .\" on kernel 2.6.13 | |
154 | The underlying file system does not support extending | |
155 | a file beyond its current size. | |
156 | .TP | |
fea681da MK |
157 | .B EROFS |
158 | The named file resides on a read-only file system. | |
159 | .TP | |
160 | .B ETXTBSY | |
161 | The file is a pure procedure (shared text) file that is being executed. | |
162 | .PP | |
163 | For | |
310b7919 | 164 | .BR ftruncate () |
fea681da MK |
165 | the same errors apply, but instead of things that can be wrong with |
166 | .IR path , | |
3ade1aa9 | 167 | we now have things that can be wrong with the file descriptor, |
fea681da MK |
168 | .IR fd : |
169 | .TP | |
170 | .B EBADF | |
fea681da MK |
171 | .I fd |
172 | is not a valid descriptor. | |
173 | .TP | |
174 | .BR EBADF " or " EINVAL | |
fea681da MK |
175 | .I fd |
176 | is not open for writing. | |
177 | .TP | |
178 | .B EINVAL | |
fea681da MK |
179 | .I fd |
180 | does not reference a regular file. | |
181 | .SH "CONFORMING TO" | |
97c1eac8 MK |
182 | 4.4BSD, SVr4, POSIX.1-2001 (these calls first appeared in 4.2BSD). |
183 | .\" POSIX.1-1996 has | |
184 | .\" .BR ftruncate (). | |
185 | .\" POSIX.1-2001 also has | |
186 | .\" .BR truncate (), | |
187 | .\" as an XSI extension. | |
188 | .\" .LP | |
189 | .\" SVr4 documents additional | |
190 | .\" .BR truncate () | |
191 | .\" error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK. SVr4 documents for | |
192 | .\" .BR ftruncate () | |
193 | .\" an additional EAGAIN error condition. | |
fea681da MK |
194 | .SH NOTES |
195 | The above description is for XSI-compliant systems. | |
196 | For non-XSI-compliant systems, the POSIX standard allows | |
d9bfdb9c | 197 | two behaviors for |
310b7919 | 198 | .BR ftruncate () |
fea681da MK |
199 | when |
200 | .I length | |
201 | exceeds the file length | |
202 | (note that | |
310b7919 | 203 | .BR truncate () |
fea681da MK |
204 | is not specified at all in such an environment): |
205 | either returning an error, or extending the file. | |
c13182ef MK |
206 | Like most Unix implementations, Linux follows the XSI requirement |
207 | when dealing with native file systems. | |
5b548b31 MK |
208 | However, some non-native file systems do not permit |
209 | .BR truncate () | |
c13182ef | 210 | and |
5b548b31 MK |
211 | .BR ftruncate () |
212 | to be used to extend a file beyond its current length: | |
213 | a notable example on Linux is VFAT. | |
fea681da MK |
214 | .\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002 |
215 | .SH "SEE ALSO" | |
216 | .BR open (2), | |
ad7cc990 MK |
217 | .BR stat (2), |
218 | .BR path_resolution (7) |