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24b7bc57 | 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 Sat Jul 24 12:46:33 1993 by Rik Faith <faith@cs.unc.edu> | |
35 | .\" Modified Tue Oct 22 22:36:33 1996 by Eric S. Raymond <esr@thyrsus.com> | |
36 | .\" Modified Mon Dec 21 13:37:05 1998 by Andries Brouwer <aeb@cwi.nl> | |
37 | .\" Modified 7 Jan 2002, Michael Kerrisk <mtk16@ext.canterbury.ac.nz> | |
38 | .\" | |
39 | .TH TRUNCATE 2 1998-12-21 "" "Linux Programmer's Manual" | |
40 | .SH NAME | |
41 | truncate, ftruncate \- truncate a file to a specified length | |
42 | .SH SYNOPSIS | |
43 | .B #include <unistd.h> | |
44 | .sp | |
45 | .BI "int truncate(const char *" path ", off_t " length ); | |
46 | .br | |
47 | .BI "int ftruncate(int " fd ", off_t " length ); | |
48 | .SH DESCRIPTION | |
49 | The | |
50 | .B truncate | |
51 | and | |
52 | .B ftruncate | |
53 | functions cause the regular file named by | |
54 | .I path | |
55 | or referenced by | |
56 | .I fd | |
57 | to be truncated to a size of precisely | |
58 | .I length | |
59 | bytes. | |
60 | .LP | |
61 | If the file previously was larger than this size, the extra data is lost. | |
62 | If the file previously was shorter, it is extended, and | |
63 | the extended part reads as zero bytes. | |
64 | .LP | |
65 | The file pointer is not changed. | |
66 | .LP | |
67 | With | |
68 | .BR ftruncate , | |
69 | the file must be open for writing; with | |
70 | .BR truncate , | |
71 | the file must be writable. | |
72 | .SH "RETURN VALUE" | |
73 | On success, zero is returned. On error, \-1 is returned, and | |
74 | .I errno | |
75 | is set appropriately. | |
76 | .SH ERRORS | |
77 | For | |
78 | .BR truncate : | |
79 | .TP | |
80 | .B EACCES | |
81 | Search permission is denied for a component of the path prefix, | |
82 | or the named file is not writable by the user. | |
83 | .TP | |
84 | .B EFAULT | |
85 | .I Path | |
86 | points outside the process's allocated address space. | |
87 | .TP | |
88 | .B EFBIG | |
89 | The argument | |
90 | .I length | |
91 | is larger than the maximum file size. (XSI) | |
92 | .TP | |
93 | .B EINTR | |
94 | A signal was caught during execution. | |
95 | .TP | |
96 | .B EINVAL | |
97 | The argument | |
98 | .I length | |
99 | is negative or larger than the maximum file size. | |
100 | .TP | |
101 | .B EIO | |
102 | An I/O error occurred updating the inode. | |
103 | .TP | |
104 | .B EISDIR | |
105 | The named file is a directory. | |
106 | .TP | |
107 | .B ELOOP | |
108 | Too many symbolic links were encountered in translating the pathname. | |
109 | .TP | |
110 | .B ENAMETOOLONG | |
111 | A component of a pathname exceeded 255 characters, | |
112 | or an entire path name exceeded 1023 characters. | |
113 | .TP | |
114 | .B ENOENT | |
115 | The named file does not exist. | |
116 | .TP | |
117 | .B ENOTDIR | |
118 | A component of the path prefix is not a directory. | |
119 | .TP | |
120 | .B EROFS | |
121 | The named file resides on a read-only file system. | |
122 | .TP | |
123 | .B ETXTBSY | |
124 | The file is a pure procedure (shared text) file that is being executed. | |
125 | .PP | |
126 | For | |
127 | .B ftruncate | |
128 | the same errors apply, but instead of things that can be wrong with | |
129 | .IR path , | |
130 | we now have things that can be wrong with | |
131 | .IR fd : | |
132 | .TP | |
133 | .B EBADF | |
134 | The | |
135 | .I fd | |
136 | is not a valid descriptor. | |
137 | .TP | |
138 | .BR EBADF " or " EINVAL | |
139 | The | |
140 | .I fd | |
141 | is not open for writing. | |
142 | .TP | |
143 | .B EINVAL | |
144 | The | |
145 | .I fd | |
146 | does not reference a regular file. | |
147 | .SH "CONFORMING TO" | |
148 | 4.4BSD, SVr4 (these function calls first appeared in BSD 4.2). | |
149 | POSIX 1003.1-1996 has | |
150 | .BR ftruncate . | |
151 | POSIX 1003.1-2001 also has | |
152 | .IR truncate , | |
153 | as an XSI extension. | |
154 | .LP | |
155 | SVr4 documents additional | |
156 | .B truncate | |
157 | error conditions EMFILE, EMULTIHP, ENFILE, ENOLINK. SVr4 documents for | |
158 | .B ftruncate | |
159 | an additional EAGAIN error condition. | |
160 | .SH NOTES | |
161 | The above description is for XSI-compliant systems. | |
162 | For non-XSI-compliant systems, the POSIX standard allows | |
163 | two behaviours for | |
164 | .B ftruncate | |
165 | when | |
166 | .I length | |
167 | exceeds the file length | |
168 | (note that | |
169 | .B truncate | |
170 | is not specified at all in such an environment): | |
171 | either returning an error, or extending the file. | |
172 | (Most Unices follow the XSI requirement.) | |
173 | .\" At the very least: OSF/1, Solaris 7, and FreeBSD conform, mtk, Jan 2002 | |
174 | .SH "SEE ALSO" | |
175 | .BR open (2) |