1. About

• https://www.computerhope.com/unix/ush.htm

1.1. Variables

Table 1.6. Variables

Command	Description
$PATH	path
$IFS	field separator
${varname:-}	default value for variable (if empty)
$0	program name
$1, $2, $3, ..., $n	arguments
$@	current command
$?	exit status from previous command
$PS1	prompt

1.2. Symbols

• ` - tick mark

• " - double quote

Table 1.7. Variables

Command	Description
!
#
$()
&&
&
'
*
+
,
-
:
;
<<
<=
<
>=
>>
>
@
[]
\\
|
||
~

1.3. Control Flow

Table 1.8. Control Flow

Command	Description
for ... do ... done
case ... esac
if ... then ... else ... fi
cat > ... << EOF ... EOF
while
until
set
unset
return
getopt
getopts
function
for
fi
false
true
expr
exec
eval
esac
else
elif
do
done
continue
case
break

1.4. Commands

Table 1.9. Shell Programming

Command	Type	Description
run-parts		run scripts or programs in a directory
seq		print a sequence of numbers
unalias
unset
uuidgen		create a new UUID value
xargs		build and execute command lines from standard input
type
trap
test		check file types and compare values
source
set +e
set -e
set
sleep		delay for a specified amount of time
sleep		sleep for a specified number of seconds
readonly
exit 0
exit 1
exit		terminate the calling process
exit		cause normal process termination
crontab		maintain crontab files for individual users (Vixie Cron)
crontab		tables for driving cron
cron		daemon to execute scheduled commands (Vixie Cron)
as		the portable GNU assembler.
alias		Creates user defined alias
awk		pattern scanning and processing language
basename		strip directory and suffix from filenames
basename		parse pathname components