Linux in a Nutshell, Fifth Edition

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Chapter 6: The Bash Shell and Korn Shell

This is the Title of the Book, eMatter Edition

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

exec

exec [command args ...]

exec [-a name] [-cl] [command args ... ]

Execute command in place of the current process (instead of

creating a new process). exec is also useful for opening, closing, or

copying file descriptors. The second form is for ksh93 and Bash.

Options

-a Use name for the value of argv[0].

-c Clear the environment before executing the program.

-l Place a minus sign at the front of argv[0], just as login(1) does.

Bash only.

Examples

trap 'exec 2>&-' 0 Close standard error when

shell script exits (signal 0)

$ exec /bin/csh Replace shell with C shell

$ exec < infile Reassign standard input to infile

exit

exit [n]

Exit a shell script with status n (e.g., exit 1). n can be 0 (success) or

nonzero (failure). If n is not given, exit status is that of the most

recent command. exit can be issued at the command line to close a

window (log out). Exit statuses can range in value from 0 to 255.

Example

if [ $# -eq 0 ]

then

echo "Usage: $0 [-c] [-d] file(s)" 1>&2

exit 1 # Error status

fi

export

export [variables]

export [name=[value] ...]

export -p

export [-fn] [name=[value] ...]

Pass (export) the value of one or more shell variables, giving global

meaning to the variables (which are local by default). For example,

a variable defined in one shell script ...