[patch] clone.2, execve.2: Describe interaction of execve(2) andCLONE_FILES

[Kevin Easton]

Hi Michael,

This very small patch against man-pages-3.50 adds a description of the
way in which a shared file descriptor table, as created by the
CLONE_FILES flag of clone(2), is unshared when a process calls execve(2).

It's easy to see this from the source - there's an unshare_files()
call early in do_execve_common().

    - Kevin

diff -urN man-pages-3.50.orig/man2/clone.2 man-pages-3.50/man2/clone.2
--- man-pages-3.50.orig/man2/clone.2    2013-03-15 18:17:35.000000000 +1100
+++ man-pages-3.50/man2/clone.2 2013-03-28 21:50:04.745932956 +1100
@@ -180,6 +180,9 @@
 .BR fcntl (2)
 .B F_SETFD
 operation), the other process is also affected.
+If a process sharing a file descriptor table calls
+.BR execve (2),
+its file descriptor table is duplicated (unshared).

 If
 .B CLONE_FILES
diff -urN man-pages-3.50.orig/man2/execve.2 man-pages-3.50/man2/execve.2
--- man-pages-3.50.orig/man2/execve.2   2013-03-15 18:17:35.000000000 +1100
+++ man-pages-3.50/man2/execve.2    2013-03-28 22:02:56.793844616 +1100
@@ -204,6 +204,11 @@
 .B SIGCHLD
 (see
 .BR clone (2)).
+.IP *
+The file descriptor table is unshared, undoing the effect of the
+.B CLONE_FILES
+flag of
+.BR clone (2).
 .PP
 Note the following further points:
 .IP * 3

diff -urN man-pages-3.50.orig/man2/clone.2 man-pages-3.50/man2/clone.2
--- man-pages-3.50.orig/man2/clone.2	2013-03-15 18:17:35.000000000 +1100
+++ man-pages-3.50/man2/clone.2	2013-03-28 21:50:04.745932956 +1100
@@ -180,6 +180,9 @@
 .BR fcntl (2)
 .B F_SETFD
 operation), the other process is also affected.
+If a process sharing a file descriptor table calls
+.BR execve (2),
+its file descriptor table is duplicated (unshared).
 
 If
 .B CLONE_FILES
diff -urN man-pages-3.50.orig/man2/execve.2 man-pages-3.50/man2/execve.2
--- man-pages-3.50.orig/man2/execve.2	2013-03-15 18:17:35.000000000 +1100
+++ man-pages-3.50/man2/execve.2	2013-03-28 22:02:56.793844616 +1100
@@ -204,6 +204,11 @@
 .B SIGCHLD
 (see
 .BR clone (2)).
+.IP *
+The file descriptor table is unshared, undoing the effect of the
+.B CLONE_FILES
+flag of
+.BR clone (2).
 .PP
 Note the following further points:
 .IP * 3