Man pages for the openat(2), fexecve(2) and related syscalls.

Reviewed by:	ru

1 files changed, 76 insertions, 9 deletions

diff --git a/lib/libc/sys/open.2 b/lib/libc/sys/open.2
index 423cf8b..8fc6d76 100644
--- a/lib/libc/sys/open.2
+++ b/lib/libc/sys/open.2
@@ -28,23 +28,25 @@
 .\"     @(#)open.2	8.2 (Berkeley) 11/16/93
 .\" $FreeBSD$
 .\"
-.Dd January 7, 2007
+.Dd April 10, 2008
 .Dt OPEN 2
 .Os
 .Sh NAME
-.Nm open
-.Nd open or create a file for reading or writing
+.Nm open , openat
+.Nd open or create a file for reading, writing or executing
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
 .In fcntl.h
 .Ft int
 .Fn open "const char *path" "int flags" "..."
+.Ft int
+.Fn openat "int fd" "const char *path" "int flags" "..."
 .Sh DESCRIPTION
 The file name specified by
 .Fa path
 is opened
-for reading and/or writing as specified by the
+for either execution or reading and/or writing as specified by the
 argument
 .Fa flags
 and the file descriptor returned to the calling process.
@@ -56,7 +58,9 @@ created if it does not exist (by specifying the
 flag).
 In this case
 .Fn open
-requires a third argument
+and
+.Fn openat
+require an additional argument
 .Fa "mode_t mode" ,
 and the file is created with mode
 .Fa mode
@@ -65,6 +69,32 @@ as described in
 and modified by the process' umask value (see
 .Xr umask 2 ) .
 .Pp
+The
+.Fn openat
+function is equivalent to the
+.Fn open
+function except in the case where the
+.Fa path
+specifies a relative path.
+In this case the file to be opened is determined relative to the directory
+associated with the file descriptor
+.Fa fd
+instead of the current working directory.
+The
+.Fa flag
+parameter and the optional fourth parameter correspond exactly to
+the parameters of
+.Fn open .
+If
+.Fn openat
+is passed the special value
+.Dv AT_FDCWD
+in the
+.Fa fd
+parameter, the current working directory is used
+and the behavior is identical to a call to
+.Fn open .
+.Pp
 The flags specified are formed by
 .Em or Ns 'ing
 the following values
@@ -73,6 +103,7 @@ the following values
 O_RDONLY	open for reading only
 O_WRONLY	open for writing only
 O_RDWR		open for reading and writing
+O_EXEC		open for execute only
 O_NONBLOCK	do not block on open
 O_APPEND	append on each write
 O_CREAT		create file if it does not exist
@@ -180,7 +211,7 @@ system call will not assign controlling terminals on
 If successful,
 .Fn open
 returns a non-negative integer, termed a file descriptor.
-It returns -1 on failure.
+It returns \-1 on failure.
 The file pointer used to mark the current position within the
 file is set to the beginning of the file.
 .Pp
@@ -202,8 +233,10 @@ system call returns the current system limit.
 .Sh RETURN VALUES
 If successful,
 .Fn open
-returns a non-negative integer, termed a file descriptor.
-It returns -1 on failure, and sets
+and
+.Fn openat
+return a non-negative integer, termed a file descriptor.
+They return \-1 on failure, and set
 .Va errno
 to indicate the error.
 .Sh ERRORS
@@ -346,13 +379,32 @@ An attempt was made to open a descriptor with an illegal combination
 of
 .Dv O_RDONLY ,
 .Dv O_WRONLY ,
+.Dv O_RDWR
 and
-.Dv O_RDWR .
+.Dv O_EXEC.
+.It Bq Eq EBADF
+The
+.Fa path
+argument does not specify an absolute path and the
+.Fa fd
+argument is
+neither
+.Dv AT_FDCWD
+nor a valid file descriptor open for searching.
+.It Bq Eq ENOTDIR
+The
+.Fa path
+argument is not an absolute path and
+.Fa fd
+is neither
+.Dv AT_FDCWD
+nor a file descriptor associated with a directory.
 .El
 .Sh SEE ALSO
 .Xr chmod 2 ,
 .Xr close 2 ,
 .Xr dup 2 ,
+.Xr fexecve 2 ,
 .Xr fhopen 2 ,
 .Xr getdtablesize 2 ,
 .Xr getfh 2 ,
@@ -367,3 +419,18 @@ The
 .Fn open
 function appeared in
 .At v6 .
+The
+.Fn openat
+function was introduced in
+.Fx 8.0 .
+.Sh BUGS
+The Open Group Extended API Set 2 specification requires that the test
+for whether
+.Fa fd
+is searchable is based on whether
+.Fa fd
+is open for searching, not whether the underlying directory currently
+permits searches.
+The present implementation of the
+.Fa openat
+checks the current permissions of directory instead.