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manual: document posix_openpt (bug 17010)

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State that getpt is similar to posix_openpt.  Use posix_openpt
instead of getpt in example.

Signed-off-by: Gavin Smith <gavinsmith0123@gmail.com>
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Gavin Smith 2023-04-12 13:45:07 +01:00 committed by Adhemerval Zanella
parent a3461d4923
commit e91c7b53c4
1 changed files with 33 additions and 3 deletions
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36
manual/terminal.texi
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@ -1947,6 +1947,33 @@ This subsection describes functions for allocating a pseudo-terminal,
and for making this pseudo-terminal available for actual use. These
functions are declared in the header file @file{stdlib.h}.
@deftypefun int posix_openpt (int @var{flags})
@standards{POSIX.1, stdlib.h}
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{@acsfd{}}}
@code{posix_openpt} returns a new file descriptor for the next
available master pseudo-terminal. In the case of an error, it returns
a value of @math{-1} instead, and sets @code{errno} to indicate
the error. @xref{Opening and Closing Files} for possible values
of @code{errno}.
@var{flags} is a bit mask created from a bitwise OR of zero or more
of the following flags:
@table @code
@item O_RDWR
Open the device for both reading and writing. It is usual to specify
this flag.
@item O_NOCTTY
Do not make the device the controlling terminal for the process.
@end table
These flags are defined in @file{fcntl.h}. @xref{Access Modes}.
For this function to be available, @code{_XOPEN_SOURCE} must be defined
to a value greater than @samp{600}. @xref{Feature Test Macros}.
@end deftypefun
@deftypefun int getpt (void)
@standards{GNU, stdlib.h}
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{@acsfd{}}}
@ -1957,6 +1984,10 @@ functions are declared in the header file @file{stdlib.h}.
@c a devfs, and returns the fd; static variables devpts_mounted and
@c have_no_dev_ptmx are safely initialized so as to avoid repeated
@c tests.
@code{getpt} is similar to @code{posix_openpt}. This function is a
GNU extension and should not be used in portable programs.
The @code{getpt} function returns a new file descriptor for the next
available master pseudo-terminal. The normal return value from
@code{getpt} is a non-negative integer file descriptor. In the case of
@ -1967,8 +1998,6 @@ an error, a value of @math{-1} is returned instead. The following
@item ENOENT
There are no free master pseudo-terminals available.
@end table
This function is a GNU extension.
@end deftypefun
@deftypefun int grantpt (int @var{filedes})
@ -2118,6 +2147,7 @@ This function is a GNU extension.
@end deftypefun
Typical usage of these functions is illustrated by the following example:
@smallexample
int
open_pty_pair (int *amaster, int *aslave)
@ -2125,7 +2155,7 @@ open_pty_pair (int *amaster, int *aslave)
int master, slave;
char *name;
master = getpt ();
master = posix_openpt (O_RDWR | O_NOCTTY);
if (master < 0)
return 0;