Why are the valid signals for / bin / kill different from kill?
I am trying to write a quick bash script to signal a program at a specific state detected by the script, and out of habit I use the full path to some of the binaries, i.e. /bin/rm
and /bin/kill
instead of rm
and kill
. However, with help kill
I noticed a difference in the valid signals that I can send and this is confusing me:
[root@linux]# which kill
/bin/kill
[root@linux]# /bin/kill -l
HUP INT QUIT ILL ABRT FPE KILL SEGV PIPE ALRM TERM USR1 USR2 CHLD CONT
STOP TSTP TTIN TTOU TRAP IOT BUS SYS STKFLT URG IO POLL CLD XCPU XFSZ
VTALRM PROF PWR WINCH UNUSED
[root@linux]# kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL
5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE
9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2
13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT
17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU
25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH
29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN
35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3 38) SIGRTMIN+4
39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12
47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14
51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10
55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6
59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX
I don't have any aliases for kill:
[root@linux]# alias
alias cp='cp -i'
alias l.='ls -d .* --color=tty'
alias ll='ls -l --color=tty'
alias ls='ls --color=tty'
alias mv='mv -i'
alias rm='rm -i'
alias vi='vim'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
Obviously the fix is to just use it kill
, but why are they different if which kill
allowed before /bin/kill
anyway?
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kill
is bash builtin. Unfortunately bash doesn't have a built-in which
(like the one zsh
that immediately tells me that kill is a shell built-in), and /usr/bin/which
has no way of knowing about your shell built-in. (I hope it bash
has something equivalent for quick checks to see if a command is inline or not. Successfull is help kill
good enough for interactive use though).
As @chepner explained in a comment, type -a COMMAND
can be used to get a list of available choices for COMMAND
: builtins, aliases, functions, and binaries in any directory on PATH
:
$ type -a kill
kill is a shell builtin
kill is /bin/kill
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