Linux in a Nutshell, Fifth Edition

type | 691

Bash and Korn

This is the Title of the Book, eMatter Edition

Copyright © 2006 O’Reilly & Associates, Inc. All rights reserved.

prefix). In addition, the shells support “pseudo-signals,” signal

names or numbers that aren’t real operating system signals but

which direct the shell to perform a specific action. These signals

are:

DEBUG

Execution of any command.

ERR

Nonzero exit status.

EXIT

Exit from shell (usually when shell script finishes).

0 Same as EXIT, for historical compatibility with the Bourne

shell.

KEYBD

A key has been read in emacs, gmacs,orvi editing mode.

ksh93 only.

RETURN

A return is executed, or a script run with

. (dot) or source

finishes. Bash only.

Examples

trap "" INT Ignore interrupts (signal 2)

trap INT Obey interrupts again

Remove a $tmp file when the shell program exits, or if the user logs

out, presses Ctrl-C, or does a kill:

trap "rm -f $tmp; exit" EXIT HUP INT TERM POSIX style

trap "rm -f $tmp; exit" 0 1 2 15 Pre-POSIX Bourne shell style

Print a “clean up” message when the shell program receives signals

SIGHUP, SIGINT, or SIGTERM:

trap 'echo Interrupt! Cleaning up...' HUP INT TERM

true

true

ksh88 alias for :. Bash and ksh93 built-in command that exits with

a true return value.

type

type [-afpPt] commands

Bash version. Show whether each command name is a Unix

command, a built-in command, an alias, a shell keyword, or a

defined shell function.

Options

-a Print all locations in $PATH