cttyhack: document the need to setsid

function                                             old     new   delta
packed_usage                                       26988   27057     +69

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 23 insertions, 4 deletions

diff --git a/include/usage.h b/include/usage.h
index 9d9ad008b..be52f187f 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -649,8 +649,16 @@
      "\n        -S SALT" \
         ) \
 
-#define cttyhack_trivial_usage NOUSAGE_STR
-#define cttyhack_full_usage ""
+#define cttyhack_trivial_usage \
+       "PROG ARGS"
+#define cttyhack_full_usage "\n\n" \
+       "Give PROG a controlling tty if possible." \
+     "\nExample for /etc/inittab (for busybox init):" \
+     "\n        ::respawn:/bin/cttyhack /bin/sh" \
+     "\nGiving controlling tty to shell running with PID 1:" \
+     "\n        $ exec cttyhack sh" \
+     "\nStarting an interative shell from boot shell script:" \
+     "\n        setsid cttyhack sh" \
 
 #define cut_trivial_usage \
        "[OPTIONS] [FILE]..."
diff --git a/shell/Config.in b/shell/Config.in
index 3b1650615..36a931715 100644
--- a/shell/Config.in
+++ b/shell/Config.in
@@ -354,9 +354,20 @@ config CTTYHACK
           It analyzes stdin with various ioctls, trying to determine whether
           it is a /dev/ttyN or /dev/ttySN (virtual terminal or serial line).
           If it detects one, it closes stdin/out/err and reopens that device.
-          Then it executes given program. Usage example for /etc/inittab
-          (for busybox init):
+          Then it executes given program. Opening the device will make
+          that device a controlling tty. This may require cttyhack
+          to be a session leader.
+
+          Example for /etc/inittab (for busybox init):
 
           ::respawn:/bin/cttyhack /bin/sh
 
+          Giving controlling tty to shell running with PID 1:
+
+          $ exec cttyhack sh
+
+          Starting an interative shell from boot shell script:
+
+          setsid cttyhack sh
+
 endmenu