Some Preset Aliases

Alias	Value	Definition
autoload	typeset –fu	define an autoloading function
echo	print –	display arguments
functions	typeset –f	display list of functions
hash	alias –t –	display list of tracked aliases
history	fc –l	list commands from history file
integer	typeset –i	declare integer variable
r	fc –e –	re-execute previous command
stop	kill –STOP	suspend job
type	whence –v	display information about commands

CONDITIONAL EXPRESSIONS

The [[...]] command is used to evaluate conditional expressions with file attributes, strings, and integers. The basic format is:

                 [[ expression ]]

where expression is the condition you are evaluating. There must be whitespace after the opening brackets, and before the closing brackets. Whitespace must also separate the expression arguments and operators. If the expression evaluates to true, then a zero exit status is returned, otherwise the expression evaluates to false and a non-zero exit status is returned.

[[...]] String Operators

–n string	true if length of string is not zero
–o option	true if option is set
–z string	true if length of string is zero
string1 = string2	true if string1 is equal to string2
string1 != string2	true if string1 is not equal to string2
string = pattern	true if string matches pattern
string != pattern	true if string does not match pattern
string1 < string2	true if string1 is less than string2
string1 > string2	true if string1 is greater than string2

[[...]] File Operators

–a file	true if file exists
–b file	true if file exists and is a block special file
–c file	true if file exists and is a character special file
–d file	true if file exists and is a directory
–f file	true if file exists is a regular file
–g file	true if file exists and its setgid bit is set
–G file	true if file exists and its group id matches the current effective group id
–k file	true if file exists and its sticky bit is set
–L file	true if file exists and is a symbolic link
–O file	true if file exists and is owned by the effective user id
–p file	true if file exists and is a fifo special file or a pipe
–r file	true if file exists and is readable
–s file	true if file exists and its size is greater than zero
–S file	true if file exists and is a socket
–t n	true if file descriptor n is open and associated with a terminal device
–u file	true if file exists and its set user-id bit is set
–w file	true if file exists and is writable
–x file	true if file exists and is executable. If file is a directory, then true indicates that the directory is readable.
file1 –ef file2	true if file1 and file2 exist and refer to the same file
file1 –nt file2	true if file1 exists and is newer than file2
file1 –ot file2	true if file1 exists and is older than file2

[[...]] Integer Operators

exp1 –eq exp2	true if exp1 is equal to exp2
exp1 –ne exp2	true if exp1 is not equal to exp2
exp1 –le exp2	true if exp1 is less than or equal to exp2
exp1 –lt exp2	true if exp1 is less than exp2
exp1 –ge exp2	true if exp1 is greater than or equal to exp2
exp1 –gt exp2	true if exp1 is greater than exp2

Other [[...]] Operators

!expression	true if expression is false
(expression)	true if expression is true; used to group expressions
[[ expression1 && expression2 ]]	true if both expression1 and expression2 are true
[[ expression1 \|\| expression2 ]]	true either expression1 or expression2 are true

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