svn commit: trunk/busybox: coreutils docs include

vda at vda at
Sun Jan 6 06:27:18 UTC 2008

Author: vda
Date: 2008-01-05 22:27:17 -0800 (Sat, 05 Jan 2008)
New Revision: 20806

tac: new applet. ~240 bytes.

Copyright (C) 2003  Yang Xiaopeng  <yxp at>
Copyright (C) 2007  Natanael Copa  <natanael.copa at>
Copyright (C) 2007  Tito Ragusa    <farmatito at>


Modified: trunk/busybox/coreutils/
--- trunk/busybox/coreutils/	2008-01-06 03:26:53 UTC (rev 20805)
+++ trunk/busybox/coreutils/	2008-01-06 06:27:17 UTC (rev 20806)
@@ -579,6 +579,12 @@
 	  sync is used to flush filesystem buffers.
+config TAC
+	bool "tac"
+	default n
+	help
+	  tac is used to concatenate and print files in reverse.
 config TAIL
 	bool "tail"
 	default n

Modified: trunk/busybox/coreutils/Kbuild
--- trunk/busybox/coreutils/Kbuild	2008-01-06 03:26:53 UTC (rev 20805)
+++ trunk/busybox/coreutils/Kbuild	2008-01-06 06:27:17 UTC (rev 20806)
@@ -66,6 +66,7 @@
 lib-$(CONFIG_STTY)      += stty.o
 lib-$(CONFIG_SUM)       += sum.o
 lib-$(CONFIG_SYNC)      += sync.o
+lib-$(CONFIG_TAC)       += tac.o
 lib-$(CONFIG_TAIL)      += tail.o
 lib-$(CONFIG_TEE)       += tee.o
 lib-$(CONFIG_TEST)      += test.o

Modified: trunk/busybox/docs/nofork_noexec.txt
--- trunk/busybox/docs/nofork_noexec.txt	2008-01-06 03:26:53 UTC (rev 20805)
+++ trunk/busybox/docs/nofork_noexec.txt	2008-01-06 06:27:17 UTC (rev 20806)
@@ -2,7 +2,7 @@
 Unix shells traditionally execute some commands internally in the attempt
 to dramatically speed up execution. It will be slow as hell if for every
-"echo blah" shell will fork and exec /bin/echo. For this end, shells
+"echo blah" shell will fork and exec /bin/echo. To this end, shells
 have to _reimplement_ these commands internally.
 Busybox is unique in this regard because it already is a collection
@@ -11,15 +11,21 @@
 are exactly those applets which are eligible for these tricks.
 Applet will be subject to NOFORK/NOEXEC tricks if it is marked as such
-in applets.h. CONFIG_FEATURE_PREFER_APPLETS is a config option which
+in applets.h. FEATURE_PREFER_APPLETS is a config option which
 globally enables usage of NOFORK/NOEXEC tricks.
+If it is enabled, FEATURE_SH_STANDALONE can be enabled too,
+and then shells will use NOFORK/NOEXEC tricks for ordinary commands.
+NB: shell builtins use these tricks regardless of FEATURE_SH_STANDALONE
-If you want to call a program and wait for it, use spawn_and_wait(argv).
-It will check whether argv[0] is an applet name and will optionally
-do NOFORK/NOEXEC thing.
+In C, if you want to call a program and wait for it, use
+spawn_and_wait(argv), BB_EXECVP(prog,argv) or BB_EXECLP(prog,argv0,...).
+They check whether program name is an applet name and optionally
+do NOFORK/NOEXEC thing depending on configuration.
 NOEXEC applet should work correctly if another applet forks and then
 executes exit(<applet>_main(argc,argv)) in the child. The rules
 roughly are:
@@ -32,10 +38,11 @@
 * ...
 NOEXEC applets save only one half of fork+exec overhead.
-NOEXEC trick is disabled for NOMMU compile.
+NOEXEC trick is disabled for NOMMU build.
 NOFORK applet should work correctly if another applet simply runs
 <applet>_main(argc,argv) and then continues with its business (xargs,
 find, shells can do it). This poses much more serious limitations
@@ -55,6 +62,8 @@
 * if you allocate memory, you can use xmalloc() only on the very first
   allocation. All other allocations should use malloc[_or_warn]().
   After first allocation, you cannot use any xfuncs.
+  Otherwise, failing xfunc will return to caller applet
+  without freeing malloced data!
 * All allocated data, opened files, signal handlers, termios settings,
   O_NONBLOCK flags etc should be freed/closed/restored prior to return.
 * ...

Modified: trunk/busybox/include/applets.h
--- trunk/busybox/include/applets.h	2008-01-06 03:26:53 UTC (rev 20805)
+++ trunk/busybox/include/applets.h	2008-01-06 06:27:17 UTC (rev 20806)
@@ -334,6 +334,7 @@

Modified: trunk/busybox/include/usage.h
--- trunk/busybox/include/usage.h	2008-01-06 03:26:53 UTC (rev 20805)
+++ trunk/busybox/include/usage.h	2008-01-06 06:27:17 UTC (rev 20806)
@@ -3542,6 +3542,11 @@
        "$ syslogd -R masterlog:514\n" \
        "$ syslogd -R\n"
+#define tac_trivial_usage \
+	"[FILE]..."
+#define tac_full_usage \
+	"Concatenates FILE(s) and prints them to stdout in reverse"
 #define tail_trivial_usage \
        "[OPTION]... [FILE]..."
 #define tail_full_usage \

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