STANDARD INPUT

None.

INPUT FILES

None.

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of kill:

LANG

This variable shall determine the locale to use for the locale categories when both LC_ALL and the corresponding environment variable (beginning with LC_ ) do not specify a locale. See 2.6.

LC_ALL

This variable shall determine the locale to be used to override any values for locale categories specified by the settings of LANG or any environment variables beginning with LC_.

LC_CTYPE

This variable shall determine the locale for the interpretation of sequences of bytes of text data as characters (e.g., single- versus multibyte characters in arguments).

LC_MESSAGES

This variable shall determine the language in which messages should be written.

ASYNCHRONOUS EVENTS

Default.

STANDARD OUTPUT

When the −l option is not specified, the standard output shall not be used. When the −l option is specified, the symbolic name of each signal shall be written in the following format: "%s%c", <signal_name>, <separator> where the <signal_name> is in uppercase, without the SIG prefix, and the

<separator> shall be either a <newline> or a <space>. For the last signal written, <separator> shall be a <newline>. When both the −l option and exit_status operand are specified, the symbolic name of the corresponding signal shall be written in the following format: "%s\n", <signal_name>

STANDARD ERROR

Used only for diagnostic messages.

OUTPUT FILES

None.

EXAMPLES

Any of the commands kill −9 100 -165 kill −s kill 100 -165 kill −s KILL 100 -165 sends the SIGKILL signal to the process whose process ID is 100 and to all processes whose process group ID is 165, assuming the sending process has permission to send that signal to the specified processes, and that they exist. POSIX. 1 {8} and POSIX. 2 do not require specific signal numbers for any signal_names. Even the −signal_number option provides symbolic (although

numeric) names for signals. If a process is terminated by a signal, its exit status indicates the signal that killed it, but the exact values are not specified. The kill −l option, however, can be used to map decimal signal numbers and exit status values into the name of a signal. The following example reports the status of a terminated job: job stat=$? if [ $stat -eq 0 ] then echo job completed successfully. elif [ $stat -gt 128 ] then echo job terminated by signal SIG $( kill -l $stat). else echo job terminated with error code $stat. fi

HISTORY OF DECISIONS MADE

The signal name extension was based on a desire to avoid limiting the kill utility to implementation-dependent values. The −l option originated from the C-shell, and is also implemented in the Korn- Shell. The C-shell output can consist of multiple output lines, because the signal names do not always fit on a single line on some terminal screens. The KornShell output also included the implementation-specific signal numbers, and was felt by the working group to be too difficult for scripts to parse conveniently. The specified output format is intended not only to accommodate the historical C-shell output, but also to permit an entirely vertical or entirely horizontal listing on systems for which this is appropriate. An earlier draft invented the name SIGNULL as a signal_name for signal 0 (used by POSIX. 1 {8} to test for the existence of a process without sending it a signal). Since the signal_name "0" can be used in this case unambiguously, SIGNULL has been removed. An earlier draft also required symbolic signal_names to be recognized with or without the SIG prefix. Historical versions of kill have not written the SIG prefix for the −l option and have not recognized the SIG prefix on signal_names. Since neither application portability nor ease of use would be improved by requiring this extension, it is no longer required. POSIX. 2 contains no utility that browses for process IDs. Values for pid are available via the ! and $ parameters of the shell command language (see 3.5.2). The use of numeric signal values was the subject of a long debate in the Working Group. During balloting, it was determined that their use should be declared obsolescent, but retained to provide backward compatibility to existing applications. Existing implementations of kill permit negative pid operands representing process groups, but this was often unclearly documented. The assumption that an

initial negative number argument specifies a signal number (rather than a process group) is the existing behavior, and was retained. Therefore, to send the default signal to a process group (say 123), an application should use a command similar to one of the following: kill - TERM -123 kill -- -123 The −s option was added in response to international interest in providing some form of kill that meets the Utility Syntax Guidelines. Some implementations provide kill only as a shell built-in utility and use that status to support the extension of killing background asynchronous lists (those started with &), by the use of job identifiers. For example, kill %1 would kill the first asynchronous list in the background. This standard does not require (but permits) such an extension, because other related job-control features are not provided by the shell, and because these facilities are not ordinarily usable in portable shell applications. This notation is expected to be introduced by the UPE.