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The "which" utility is not guaranteed to be installed either, and if it is, its behavior is not portable either. Conversely, the "command -v" shell builtin is required to exist in all POSIX 2008 compliant shells, and is thus guaranteed to work everywhere. Examples of open-source shells likely to be installed as /bin/sh on Linux, which implement the 11-year-old standard: ash, bash, busybox, dash, ksh, mksh and zsh. A side benefit of using the POSIX portable option is that it requires neither an external disk executable, nor (because unlike "which", the exit code is reliable) a subshell fork. This therefore represents a mild speedup. Signed-off-by: Eli Schwartz <eschwartz@archlinux.org> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
All executable files in this directory are processed in shell expansion order. 00_*: Reserved for 00_header. 10_*: Native boot entries. 20_*: Third party apps (e.g. memtest86+). The number namespace in-between is configurable by system installer and/or administrator. For example, you can add an entry to boot another OS as 01_otheros, 11_otheros, etc, depending on the position you want it to occupy in the menu; and then adjust the default setting via /etc/default/grub.