Working with the Unix OS

Unix Shells
if $append
then
tee -a "$output"
else
cat
fi
done
exit 0 # return a healthy exit status
Built-in Shell Commands
: null command
. execute a program or shell script
'pgm' replace with output of pgm command
break exit from for, while, or until loop
cd
change working directory
continue start with next iteration of for, while
eval scan and evaluate the command line
exec execute a program in place of current process
exit exit from current shell
export place the value of a variable in calling environment
newgrp change users group
read read a line from standard input
readonly declare a variable to be readonly
set
Set shell variables (display all variables)
shift promote each command line argument
times display times for current shell and its children
trap trap a signal
umask File creation mask
wait wait for a background process to terminate
echo display arguments
getopts parse arguments to a shell script
hash remember location of command in search path
pwd
print working directory
return exit from a function
test compare arguments
type display how each arg would be interpreted
ulimit limit the size of files written by shell
unset remove a variable or function
! Shell Variables
HOME pathname of your home directory
IFS
internal field separator
PATH search path for commands
PS1 prompt string 1
PS2 prompt string 2
MAIL file where system stores your mail
HOST the host name of the computer
SHELL identifies name of invoked shell
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