o The -s limit is ARG_MAX - 4K, not ARG_MAX - 2K.

o Mention that the current environment is part of the -s calculation.
o Add a BUGS section that warns against executing a program that increases
  the size of the argument list or the size of the environment.

  I have wondered for a while what the difference is between

    get a big list | xargs sudo command

  which fails and

    get a big list | sudo xargs command

  which succeeds.  The answer is that in the first case, sudo expands
  the environment and pushes the amount of data passed into execve over
  the E2BIG threshold.

1 files changed, 14 insertions, 4 deletions

diff --git a/usr.bin/xargs/xargs.1 b/usr.bin/xargs/xargs.1
index b7f4cdb..671edc3 100644
--- a/usr.bin/xargs/xargs.1
+++ b/usr.bin/xargs/xargs.1
@@ -112,16 +112,17 @@ is 5000.
 .It Fl s Ar size
 Set the maximum number of bytes for the command line length provided to
 .Ar utility .
-The sum of the length of the utility name and the arguments passed to
+The sum of the length of the utility name, the arguments passed to
 .Ar utility
 (including
 .Dv NULL
-terminators) will be less than or equal to this number.
+terminators) and the current environment will be less than or equal to
+this number.
 The current default value for
 .Ar size
 is
 .Dv ARG_MAX
-- 2048.
+- 4096.
 .It Fl t
 Echo the command to be executed to standard error immediately before it
 is executed.
@@ -164,10 +165,19 @@ If any other error occurs,
 exits with a value of 1.
 .Sh SEE ALSO
 .Xr echo 1 ,
-.Xr find 1
+.Xr find 1 ,
+.Xr execvp 3
 .Sh STANDARDS
 The
 .Nm
 utility is expected to be
 .St -p1003.2
 compliant.
+.Sh BUGS
+If
+.Ar utility
+attempts to envoke another command such that the number of arguments or the
+size of the environment is increased, it risks
+.Xr execvp 3
+failing with
+.Dv E2BIG .