exec.3: glibc 2.24 dropped CWD from the defaul path

Document the glibc 2.24 change that dropped CWD from the default
search path employed by execlp(), execvp() and execvpe() when
PATH is not defined.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man3/exec.3 b/man3/exec.3
index fedeef3dfa827cc3fa2ab7764d8cac20c171820c..0d531e921911c8706a178cacd1344a872cd4c72c 100644 (file)
--- a/man3/exec.3
+++ b/man3/exec.3
@@ -146,11 +146,11 @@ specified in the
 .B PATH
 environment variable.
 If this variable isn't defined, the path list defaults to
-the current directory followed by the list of directories returned by
-.IR confstr(_CS_PATH) .
-(This
-.BR confstr (3)
-call typically returns the value "/bin:/usr/bin".)
+a list that includes the directories returned by
+.IR confstr(_CS_PATH)
+(which typically returns the value "/bin:/usr/bin")
+and possibly also the current working directory;
+see NOTES for further details.
 .PP
 If the specified filename includes a slash character, then
 .B PATH
@@ -219,15 +219,27 @@ The
 .BR execvpe ()
 function is a GNU extension.
 .SH NOTES
-On some other systems, the default path (used when the environment
-does not contain the variable \fBPATH\fR) has the current working
-directory listed after
+The default search path (used when the environment
+does not contain the variable \fBPATH\fR)
+shows some variation across systems.
+It generally includes
+.I /bin
+and
+.IR /usr/bin
+(in that order) and may also include the current working directory.
+On some other systems, the current working is included after
 .I /bin
 and
 .IR /usr/bin ,
 as an anti-Trojan-horse measure.
-Linux uses here the
-traditional "current directory first" default path.
+The glibc implementation long followed the traditional default where
+the current working directory is included at the start of the search path.
+However, some code refactoring during the development of glibc 2.24
+.\" glibc commit 1eb8930608705702d5746e5491bab4e4429fcb83
+caused the current working directory to be dropped altogether
+from the default search path.
+This accidental behavior change is considered mildly beneficial,
+and won't be reverted.
 .PP
 The behavior of
 .BR execlp ()