# # For a description of the syntax of this configuration file, # see scripts/kbuild/config-language.txt. # menu "Shells" INSERT choice prompt "Choose which shell is aliased to 'sh' name" default FEATURE_SH_IS_ASH help Choose which shell you want to be executed by 'sh' alias. The ash shell is the most bash compatible and full featured one. # note: cannot use "select ASH" here, it breaks "make allnoconfig" config FEATURE_SH_IS_ASH depends on ASH bool "ash" depends on !NOMMU config FEATURE_SH_IS_HUSH depends on HUSH bool "hush" config FEATURE_SH_IS_NONE bool "none" endchoice choice prompt "Choose which shell is aliased to 'bash' name" default FEATURE_BASH_IS_NONE help Choose which shell you want to be executed by 'bash' alias. The ash shell is the most bash compatible and full featured one. Note that selecting this option does not switch on any bash compatibility code. It merely makes it possible to install /bin/bash (sym)link and run scripts which start with #!/bin/bash line. Many systems use it in scripts which use bash-specific features, even simple ones like $RANDOM. Without this option, busybox can't be used for running them because it won't recongnize "bash" as a supported applet name. config FEATURE_BASH_IS_ASH depends on ASH bool "ash" depends on !NOMMU config FEATURE_BASH_IS_HUSH depends on HUSH bool "hush" config FEATURE_BASH_IS_NONE bool "none" endchoice config LASH bool "lash (deprecated: aliased to hush)" default n select HUSH help lash is deprecated and will be removed, please migrate to hush. config MSH bool "msh (deprecated: please use hush)" default n select HUSH help msh is deprecated and will be removed, please migrate to hush. If there is a feature msh has but hush does not, please let us know. # The minix shell (adds just 30k) is quite complete and handles things # like for/do/done, case/esac and all the things you expect a Bourne # shell to do. It is not always pedantically correct about Bourne # shell grammar (try running the shell testscript "tests/sh.testcases" # on it and compare vs bash) but for most things it works quite well. # It uses only vfork, so it can be used on uClinux systems. config SH_MATH_SUPPORT bool "POSIX math support" default y depends on ASH || HUSH help Enable math support in the shell via $((...)) syntax. config SH_MATH_SUPPORT_64 bool "Extend POSIX math support to 64 bit" default y depends on SH_MATH_SUPPORT help Enable 64-bit math support in the shell. This will make the shell slightly larger, but will allow computation with very large numbers. This is not in POSIX, so do not rely on this in portable code. config FEATURE_SH_EXTRA_QUIET bool "Hide message on interactive shell startup" default y depends on HUSH || ASH help Remove the busybox introduction when starting a shell. config FEATURE_SH_STANDALONE bool "Standalone shell" default n depends on (HUSH || ASH) && FEATURE_PREFER_APPLETS help This option causes busybox shells to use busybox applets in preference to executables in the PATH whenever possible. For example, entering the command 'ifconfig' into the shell would cause busybox to use the ifconfig busybox applet. Specifying the fully qualified executable name, such as '/sbin/ifconfig' will still execute the /sbin/ifconfig executable on the filesystem. This option is generally used when creating a statically linked version of busybox for use as a rescue shell, in the event that you screw up your system. This is implemented by re-execing /proc/self/exe (typically) with right parameters. Some selected applets ("NOFORK" applets) can even be executed without creating new process. Instead, busybox will call _main() internally. However, this causes problems in chroot jails without mounted /proc and with ps/top (command name can be shown as 'exe' for applets started this way). # untrue? # Note that this will *also* cause applets to take precedence # over shell builtins of the same name. So turning this on will # eliminate any performance gained by turning on the builtin "echo" # and "test" commands in ash. # untrue? # Note that when using this option, the shell will attempt to directly # run '/bin/busybox'. If you do not have the busybox binary sitting in # that exact location with that exact name, this option will not work at # all. config FEATURE_SH_NOFORK bool "Run 'nofork' applets directly" default n depends on (HUSH || ASH) && FEATURE_PREFER_APPLETS help This option causes busybox shells [currently only ash] to not execute typical fork/exec/wait sequence, but call _main directly, if possible. (Sometimes it is not possible: for example, this is not possible in pipes). This will be done only for some applets (those which are marked NOFORK in include/applets.h). This may significantly speed up some shell scripts. This feature is relatively new. Use with care. config CTTYHACK bool "cttyhack" default y help One common problem reported on the mailing list is "can't access tty; job control turned off" error message which typically appears when one tries to use shell with stdin/stdout opened to /dev/console. This device is special - it cannot be a controlling tty. Proper solution is to use correct device instead of /dev/console. cttyhack provides "quick and dirty" solution to this problem. 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. 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 Starting an interactive shell from boot shell script: setsid cttyhack sh Giving controlling tty to shell running with PID 1: # exec cttyhack sh Without cttyhack, you need to know exact tty name, and do something like this: # exec setsid sh -c 'exec sh /dev/tty1 2>&1' endmenu