1GETCWD(P) POSIX Programmer's Manual GETCWD(P)
2
6 getcwd - get the pathname of the current working directory
7
9 #include <unistd.h>
10 char *getcwd(char *buf, size_t size);
12
15 The getcwd() function shall place an absolute pathname of the current
16 working directory in the array pointed to by buf, and return buf. The
17 pathname copied to the array shall contain no components that are sym‐
18 bolic links. The size argument is the size in bytes of the character
19 array pointed to by the buf argument. If buf is a null pointer, the
20 behavior of getcwd() is unspecified.
21
23 Upon successful completion, getcwd() shall return the buf argument.
24 Otherwise, getcwd() shall return a null pointer and set errno to indi‐
25 cate the error. The contents of the array pointed to by buf are then
26 undefined.
27
29 The getcwd() function shall fail if:
30 EINVAL The size argument is 0.
32 ERANGE The size argument is greater than 0, but is smaller than the
34 length of the pathname +1.
35 The getcwd() function may fail if:
38 EACCES Read or search permission was denied for a component of the
40 pathname.
41 ENOMEM Insufficient storage space is available.
43 The following sections are informative.
46
48 Determining the Absolute Pathname of the Current Working Directory
49 The following example returns a pointer to an array that holds the
50 absolute pathname of the current working directory. The pointer is
51 returned in the ptr variable, which points to the buf array where the
52 pathname is stored.
53 #include <stdlib.h>
56 #include <unistd.h>
57 ...
58 long size;
59 char *buf;
60 char *ptr;
61 size = pathconf(".", _PC_PATH_MAX);
64 if ((buf = (char *)malloc((size_t)size)) != NULL)
67 ptr = getcwd(buf, (size_t)size);
68 ...
69
71 None.
72
74 Since the maximum pathname length is arbitrary unless {PATH_MAX} is
75 defined, an application generally cannot supply a buf with size
76 {{PATH_MAX}+1}.
77 Having getcwd() take no arguments and instead use the malloc() function
79 to produce space for the returned argument was considered. The advan‐
80 tage is that getcwd() knows how big the working directory pathname is
81 and can allocate an appropriate amount of space. But the programmer
82 would have to use the free() function to free the resulting object, or
83 each use of getcwd() would further reduce the available memory. Also,
84 malloc() and free() are used nowhere else in this volume of
85 IEEE Std 1003.1-2001. Finally, getcwd() is taken from the SVID where it
86 has the two arguments used in this volume of IEEE Std 1003.1-2001.
87 The older function getwd() was rejected for use in this context because
89 it had only a buffer argument and no size argument, and thus had no way
90 to prevent overwriting the buffer, except to depend on the programmer
91 to provide a large enough buffer.
92 On some implementations, if buf is a null pointer, getcwd() may obtain
94 size bytes of memory using malloc(). In this case, the pointer returned
95 by getcwd() may be used as the argument in a subsequent call to free().
96 Invoking getcwd() with buf as a null pointer is not recommended in con‐
97 forming applications.
98 If a program is operating in a directory where some (grand)parent
100 directory does not permit reading, getcwd() may fail, as in most imple‐
101 mentations it must read the directory to determine the name of the
102 file. This can occur if search, but not read, permission is granted in
103 an intermediate directory, or if the program is placed in that direc‐
104 tory by some more privileged process (for example, login). Including
105 the [EACCES] error condition makes the reporting of the error consis‐
106 tent and warns the application writer that getcwd() can fail for rea‐
107 sons beyond the control of the application writer or user. Some imple‐
108 mentations can avoid this occurrence (for example, by implementing
109 getcwd() using pwd, where pwd is a set-user-root process), thus the
110 error was made optional. Since this volume of IEEE Std 1003.1-2001 per‐
111 mits the addition of other errors, this would be a common addition and
112 yet one that applications could not be expected to deal with without
113 this addition.
114
116 None.
117
119 malloc() , the Base Definitions volume of IEEE Std 1003.1-2001,
120 <unistd.h>
121
123 Portions of this text are reprinted and reproduced in electronic form
124 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
125 -- Portable Operating System Interface (POSIX), The Open Group Base
126 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
127 Electrical and Electronics Engineers, Inc and The Open Group. In the
128 event of any discrepancy between this version and the original IEEE and
129 The Open Group Standard, the original IEEE and The Open Group Standard
130 is the referee document. The original Standard can be obtained online
131 at http://www.opengroup.org/unix/online.html .
132IEEE/The Open Group 2003 GETCWD(P)