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.Dd $Mdocdate: July 25 2022 $
.Dt GETCWD 3
.Os
.Sh NAME
.Nm getcwd ,
.Nm getwd
.Nd get working directory pathname
.Sh SYNOPSIS
.In unistd.h
.Ft char *
.Fn getcwd "char *buf" "size_t size"
.Ft char *
.Fn getwd "char *buf"
.Sh DESCRIPTION
The
.Fn getcwd
function copies the absolute pathname of the current working directory
into the memory referenced by
.Fa buf
and returns a pointer to
.Fa buf .
The
.Fa size
argument is the size, in bytes, of the array referenced by
.Fa buf .
.Pp
If
.Fa buf
is not
.Dv NULL
and the length of the pathname plus the terminating NUL
character is greater than
.Fa size ,
a null pointer is returned and
.Va errno
is set to
.Dv ERANGE .
.Pp
As an extension to
.St -p1003.1-2001 ,
if
.Fa buf
is
.Dv NULL ,
space is allocated as necessary to store the pathname.
In this case, it is the responsibility of the caller to
.Xr free 3
the pointer that
.Fn getcwd
returns.
.Pp
The deprecated
.Fn getwd
function is similar to
.Fn getcwd ,
but assumes that
.Fa buf
is non-NULL and has a size of
.Dv PATH_MAX
(as defined by the include
file
.In limits.h ) .
It does not allocate memory and is provided for source compatibility only.
If the length of the pathname plus the terminating NUL
character is greater than
.Dv PATH_MAX ,
a null pointer is returned.
On error,
.Fn getwd
writes an error message into the memory referenced by
.Fa buf .
.Pp
These functions have traditionally been used by programs to save the
name of a working directory for the purpose of returning to it.
A much faster and less error-prone method of accomplishing this is to
open the current directory
.Pq Pa \&.
and use the
.Xr fchdir 2
function to return.
.Sh RETURN VALUES
Upon successful completion, a pointer to the pathname is returned.
Otherwise a null pointer is returned and
.Va errno
is set to indicate the error.
In addition,
.Fn getwd
copies the error message associated with
.Va errno
into the memory referenced by
.Fa buf .
.Sh ERRORS
The
.Fn getcwd
function will fail if:
.Bl -tag -width Er
.It Bq Er EACCES
Read or search permission was denied for a component of the pathname.
.It Bq Er EFAULT
.Fa buf
points to an invalid address.
.It Bq Er EINVAL
The
.Fa size
argument is zero.
.It Bq Er ENOENT
A component of the pathname no longer exists.
.It Bq Er ENOMEM
Insufficient memory is available.
.It Bq Er ERANGE
The
.Fa size
argument is greater than zero but smaller than the length of the pathname
plus 1.
.El
.Sh SEE ALSO
.Xr pwd 1 ,
.Xr chdir 2 ,
.Xr malloc 3 ,
.Xr strerror 3
.Sh STANDARDS
The
.Fn getcwd
function conforms to
.St -p1003.1-2001 .
The ability to specify a null pointer and have
.Fn getcwd
allocate memory as necessary is an extension.
.Sh HISTORY
The
.Fn getwd
function first appeared in
.Bx 4.0 .
The
.Fn getcwd
function first appeared in
.At V.1
and was reimplemented for
.Bx 4.3 Net/2 .
.Pp
In
.Ox 4.0 ,
.Fn getcwd
was reimplemented on top of the
.Fn __getcwd
system call.
Its calling convention differs from the standard
function by requiring
.Ar buf
to not be
.Dv NULL
and by returning an integer,
zero on success, and -1 with corresponding errno on failure.
This is visible in the output of
.Xr kdump 1 .
.Sh BUGS
The
.Fn getwd
function does not do sufficient error checking and is not able to return very
long, but valid, paths.
It is provided for compatibility only.