1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183
|
texinode(Conditional Expressions)(Prompt Expansion)(Arithmetic Evaluation)(Top)
chapter(Conditional Expressions)
ifzman(\
sect(Conditional Expressions)
)\
cindex(conditional expressions)
cindex(expressions, conditional)
A em(conditional expression) is used with the tt([[)
compound command to test attributes of files and to compare strings.
Each expression can be constructed from one or more
of the following unary or binary expressions:
startitem()
item(tt(-a) var(file))(
true if var(file) exists.
)
item(tt(-b) var(file))(
true if var(file) exists and is a block special file.
)
item(tt(-c) var(file))(
true if var(file) exists and is a character special file.
)
item(tt(-d) var(file))(
true if var(file) exists and is a directory.
)
item(tt(-e) var(file))(
true if var(file) exists.
)
item(tt(-f) var(file))(
true if var(file) exists and is a regular file.
)
item(tt(-g) var(file))(
true if var(file) exists and has its setgid bit set.
)
item(tt(-h) var(file))(
true if var(file) exists and is a symbolic link.
)
item(tt(-k) var(file))(
true if var(file) exists and has its sticky bit set.
)
item(tt(-n) var(string))(
true if length of var(string) is non-zero.
)
item(tt(-o) var(option))(
true if option named var(option) is on. var(option)
may be a single character, in which case it is a single letter option name.
(See noderef(Specifying Options).)
)
item(tt(-p) var(file))(
true if var(file) exists and is a FIFO special file (named pipe).
)
item(tt(-r) var(file))(
true if var(file) exists and is readable by current process.
)
item(tt(-s) var(file))(
true if var(file) exists and has size greater than zero.
)
item(tt(-t) var(fd))(
true if file descriptor number var(fd)
is open and associated with a terminal device.
(note: var(fd) is not optional)
)
item(tt(-u) var(file))(
true if var(file) exists and has its setuid bit set.
)
item(tt(-w) var(file))(
true if var(file) exists and is writable by current process.
)
item(tt(-x) var(file))(
true if var(file) exists and is executable by current process.
If var(file) exists and is a directory, then the current process
has permission to search in the directory.
)
item(tt(-z) var(string))(
true if length of var(string) is zero.
)
item(tt(-L) var(file))(
true if var(file) exists and is a symbolic link.
)
item(tt(-O) var(file))(
true if var(file) exists and is owned by the effective user ID of this process.
)
item(tt(-G) var(file))(
true if var(file) exists and its group matches
the effective group ID of this process.
)
item(tt(-S) var(file))(
true if var(file) exists and is a socket.
)
item(tt(-N) var(file))(
true if var(file) exists and its access time is
not newer than its modification time.
)
item(var(file1) tt(-nt) var(file2))(
true if var(file1) exists and is newer than var(file2).
)
item(var(file1) tt(-ot) var(file2))(
true if var(file1) exists and is older than var(file2).
)
item(var(file1) tt(-ef) var(file2))(
true if var(file1) and var(file2) exist and refer to the same file.
)
xitem(var(string) tt(=) var(pattern))
item(var(string) tt(==) var(pattern))(
true if var(string) matches var(pattern).
The `tt(==)' form is the preferred one. The `tt(=)' form is for
backward compatibility and should be considered obsolete.
)
item(var(string) tt(!=) var(pattern))(
true if var(string) does not match var(pattern).
)
item(var(string1) tt(<) var(string2))(
true if var(string1) comes before var(string2)
based on ASCII value of their characters.
)
item(var(string1) tt(>) var(string2))(
true if var(string1) comes after var(string2)
based on ASCII value of their characters.
)
item(var(exp1) tt(-eq) var(exp2))(
true if var(exp1) is numerically equal to var(exp2).
)
item(var(exp1) tt(-ne) var(exp2))(
true if var(exp1) is numerically not equal to var(exp2).
)
item(var(exp1) tt(-lt) var(exp2))(
true if var(exp1) is numerically less than var(exp2).
)
item(var(exp1) tt(-gt) var(exp2))(
true if var(exp1) is numerically greater than var(exp2).
)
item(var(exp1) tt(-le) var(exp2))(
true if var(exp1) is numerically less than or equal to var(exp2).
)
item(var(exp1) tt(-ge) var(exp2))(
true if var(exp1) is numerically greater than or equal to var(exp2).
)
item(tt(LPAR()) var(exp) tt(RPAR()))(
true if var(exp) is true.
)
item(tt(!) var(exp))(
true if var(exp) is false.
)
item(var(exp1) tt(&&) var(exp2))(
true if var(exp1) and var(exp2) are both true.
)
item(var(exp1) tt(||) var(exp2))(
true if either var(exp1) or var(exp2) is true.
)
enditem()
Normal shell expansion is performed on the var(file), var(string) and
var(pattern) arguments, but the result of each expansion is constrained to
be a single word, similar to the effect of double quotes. However, pattern
metacharacters are active for the var(pattern) arguments; the patterns
are the same as those used for filename generation, see
ifzman(\
zmanref(zshexpn)\
)\
ifnzman(\
noderef(Filename Generation)\
)\
, but there is no special behaviour
of `tt(/)' nor initial dots, and no glob qualifiers are allowed.
In each of the above expressions, if
var(file) is of the form `tt(/dev/fd/)var(n)',
where var(n) is an integer,
then the test applied to the open file whose
descriptor number is var(n),
even if the underlying system does not support
the tt(/dev/fd) directory.
In the forms which do numeric comparison, the expressions var(exp)
undergo arithmetic expansion as if they were enclosed in tt($((...))).
For example, the following:
example([[ ( -f foo || -f bar ) && $report = y* ]] && print File exists.)
tests if either file tt(foo) or file tt(bar) exists, and if so, if the
value of the parameter tt(report) begins with `tt(y)'; if the complete
condition is true, the message `tt(File exists.)' is printed.
|