1getcwd(3) Library Functions Manual getcwd(3)
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6 getcwd, getwd, get_current_dir_name - get current working directory
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9 Standard C library (libc, -lc)
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12 #include <unistd.h>
13 char *getcwd(char buf[.size], size_t size);
15 char *get_current_dir_name(void);
16 [[deprecated]] char *getwd(char buf[PATH_MAX]);
18 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
20 get_current_dir_name():
22 _GNU_SOURCE
23 getwd():
25 Since glibc 2.12:
26 (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200809L)
27 || /* glibc >= 2.19: */ _DEFAULT_SOURCE
28 || /* glibc <= 2.19: */ _BSD_SOURCE
29 Before glibc 2.12:
30 _BSD_SOURCE || _XOPEN_SOURCE >= 500
31
33 These functions return a null-terminated string containing an absolute
34 pathname that is the current working directory of the calling process.
35 The pathname is returned as the function result and via the argument
36 buf, if present.
37 The getcwd() function copies an absolute pathname of the current work‐
39 ing directory to the array pointed to by buf, which is of length size.
40 If the length of the absolute pathname of the current working direc‐
42 tory, including the terminating null byte, exceeds size bytes, NULL is
43 returned, and errno is set to ERANGE; an application should check for
44 this error, and allocate a larger buffer if necessary.
45 As an extension to the POSIX.1-2001 standard, glibc's getcwd() allo‐
47 cates the buffer dynamically using malloc(3) if buf is NULL. In this
48 case, the allocated buffer has the length size unless size is zero,
49 when buf is allocated as big as necessary. The caller should free(3)
50 the returned buffer.
51 get_current_dir_name() will malloc(3) an array big enough to hold the
53 absolute pathname of the current working directory. If the environment
54 variable PWD is set, and its value is correct, then that value will be
55 returned. The caller should free(3) the returned buffer.
56 getwd() does not malloc(3) any memory. The buf argument should be a
58 pointer to an array at least PATH_MAX bytes long. If the length of the
59 absolute pathname of the current working directory, including the ter‐
60 minating null byte, exceeds PATH_MAX bytes, NULL is returned, and errno
61 is set to ENAMETOOLONG. (Note that on some systems, PATH_MAX may not
62 be a compile-time constant; furthermore, its value may depend on the
63 filesystem, see pathconf(3).) For portability and security reasons,
64 use of getwd() is deprecated.
65
67 On success, these functions return a pointer to a string containing the
68 pathname of the current working directory. In the case of getcwd() and
69 getwd() this is the same value as buf.
70 On failure, these functions return NULL, and errno is set to indicate
72 the error. The contents of the array pointed to by buf are undefined
73 on error.
74
76 EACCES Permission to read or search a component of the filename was de‐
77 nied.
78 EFAULT buf points to a bad address.
80 EINVAL The size argument is zero and buf is not a null pointer.
82 EINVAL getwd(): buf is NULL.
84 ENAMETOOLONG
86 getwd(): The size of the null-terminated absolute pathname
87 string exceeds PATH_MAX bytes.
88 ENOENT The current working directory has been unlinked.
90 ENOMEM Out of memory.
92 ERANGE The size argument is less than the length of the absolute path‐
94 name of the working directory, including the terminating null
95 byte. You need to allocate a bigger array and try again.
96
98 For an explanation of the terms used in this section, see at‐
99 tributes(7).
100 ┌────────────────────────────────────────┬───────────────┬─────────────┐
102 │Interface │ Attribute │ Value │
103 ├────────────────────────────────────────┼───────────────┼─────────────┤
104 │getcwd(), getwd() │ Thread safety │ MT-Safe │
105 ├────────────────────────────────────────┼───────────────┼─────────────┤
106 │get_current_dir_name() │ Thread safety │ MT-Safe env │
107 └────────────────────────────────────────┴───────────────┴─────────────┘
108
110 POSIX.1-2001 leaves the behavior of getcwd() unspecified if buf is
111 NULL.
112 POSIX.1-2001 does not define any errors for getwd().
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116 C library/kernel differences
117 On Linux, the kernel provides a getcwd() system call, which the func‐
118 tions described in this page will use if possible. The system call
119 takes the same arguments as the library function of the same name, but
120 is limited to returning at most PATH_MAX bytes. (Before Linux 3.12,
121 the limit on the size of the returned pathname was the system page
122 size. On many architectures, PATH_MAX and the system page size are
123 both 4096 bytes, but a few architectures have a larger page size.) If
124 the length of the pathname of the current working directory exceeds
125 this limit, then the system call fails with the error ENAMETOOLONG. In
126 this case, the library functions fall back to a (slower) alternative
127 implementation that returns the full pathname.
128 Following a change in Linux 2.6.36, the pathname returned by the
130 getcwd() system call will be prefixed with the string "(unreachable)"
131 if the current directory is not below the root directory of the current
132 process (e.g., because the process set a new filesystem root using ch‐
133 root(2) without changing its current directory into the new root).
134 Such behavior can also be caused by an unprivileged user by changing
135 the current directory into another mount namespace. When dealing with
136 pathname from untrusted sources, callers of the functions described in
137 this page should consider checking whether the returned pathname starts
138 with '/' or '(' to avoid misinterpreting an unreachable path as a rela‐
139 tive pathname.
140
142 getcwd()
143 POSIX.1-2008.
144 get_current_dir_name()
146 GNU.
147 getwd()
149 None.
150
152 getcwd()
153 POSIX.1-2001.
154 getwd()
156 POSIX.1-2001, but marked LEGACY. Removed in POSIX.1-2008. Use
157 getcwd() instead.
158 Under Linux, these functions make use of the getcwd() system call
160 (available since Linux 2.1.92). On older systems they would query
161 /proc/self/cwd. If both system call and proc filesystem are missing, a
162 generic implementation is called. Only in that case can these calls
163 fail under Linux with EACCES.
164
166 These functions are often used to save the location of the current
167 working directory for the purpose of returning to it later. Opening
168 the current directory (".") and calling fchdir(2) to return is usually
169 a faster and more reliable alternative when sufficiently many file de‐
170 scriptors are available, especially on platforms other than Linux.
171
173 Since the Linux 2.6.36 change that added "(unreachable)" in the circum‐
174 stances described above, the glibc implementation of getcwd() has
175 failed to conform to POSIX and returned a relative pathname when the
176 API contract requires an absolute pathname. With glibc 2.27 onwards
177 this is corrected; calling getcwd() from such a pathname will now re‐
178 sult in failure with ENOENT.
179
181 pwd(1), chdir(2), fchdir(2), open(2), unlink(2), free(3), malloc(3)
182Linux man-pages 6.04 2023-03-30 getcwd(3)