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159 lines
4.6 KiB
Plaintext
159 lines
4.6 KiB
Plaintext
texinode(Conditional Expressions)(Compatibility)(Arithmetic Evaluation)(Top)
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chapter(Conditional Expressions)
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ifzman(\
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sect(Conditional Expressions)
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)\
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cindex(conditional expressions)
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cindex(expressions, conditional)
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A em(conditional expression) is used with the tt([[)
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compound command to test attributes of files and to compare strings.
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Each expression can be constructed from one or more
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of the following unary or binary expressions:
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startitem()
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item(tt(-a) var(file))(
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true if var(file) exists.
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)
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item(tt(-b) var(file))(
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true if var(file) exists and is a block special file.
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)
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item(tt(-c) var(file))(
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true if var(file) exists and is a character special file.
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)
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item(tt(-d) var(file))(
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true if var(file) exists and is a directory.
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)
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item(tt(-e) var(file))(
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true if var(file) exists.
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)
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item(tt(-f) var(file))(
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true if var(file) exists and is a regular file.
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)
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item(tt(-g) var(file))(
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true if var(file) exists and has its setgid bit set.
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)
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item(tt(-h) var(file))(
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true if var(file) exists and is a symbolic link.
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)
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item(tt(-k) var(file))(
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true if var(file) exists and has its sticky bit set.
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)
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item(tt(-n) var(string))(
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true if length of var(string) is non-zero.
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)
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item(tt(-o) var(option))(
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true if option named var(option) is on. var(option)
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may be a single character, in which case it is a single letter option name.
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(See noderef(Specifying Options).)
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)
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item(tt(-p) var(file))(
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true if var(file) exists and is a FIFO special file (named pipe).
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)
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item(tt(-r) var(file))(
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true if var(file) exists and is readable by current process.
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)
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item(tt(-s) var(file))(
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true if var(file) exists and has size greater than zero.
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)
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item(tt(-t) var(fd))(
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true if file descriptor number var(fd)
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is open and associated with a terminal device.
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(note: var(fd) is not optional)
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)
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item(tt(-u) var(file))(
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true if var(file) exists and has its setuid bit set.
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)
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item(tt(-w) var(file))(
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true if var(file) exists and is writable by current process.
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)
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item(tt(-x) var(file))(
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true if var(file) exists and is executable by current process.
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If var(file) exists and is a directory, then the current process
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has permission to search in the directory.
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)
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item(tt(-z) var(string))(
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true if length of var(string) is zero.
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)
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item(tt(-L) var(file))(
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true if var(file) exists and is a symbolic link.
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)
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item(tt(-O) var(file))(
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true if var(file) exists and is owned by the effective user ID of this process.
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)
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item(tt(-G) var(file))(
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true if var(file) exists and its group matches
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the effective group ID of this process.
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)
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item(tt(-S) var(file))(
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true if var(file) exists and is a socket.
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)
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item(tt(-N) var(file))(
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true if var(file) exists and its access time is
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not newer than its modification time.
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)
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item(var(file1) tt(-nt) var(file2))(
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true if var(file1) exists and is newer than var(file2).
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)
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item(var(file1) tt(-ot) var(file2))(
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true if var(file1) exists and is older than var(file2).
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)
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item(var(file1) tt(-ef) var(file2))(
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true if var(file1) and var(file2) exist and refer to the same file.
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)
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xitem(var(string) tt(=) var(pattern))
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item(var(string) tt(==) var(pattern))(
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true if var(string) matches var(pattern).
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The `tt(==)' form is the preferred one. The `tt(=)' form is for
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backward compatibility and should be considered obsolete.
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)
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item(var(string) tt(!=) var(pattern))(
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true if var(string) does not match var(pattern).
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)
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item(var(string1) tt(<) var(string2))(
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true if var(string1) comes before var(string2)
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based on ASCII value of their characters.
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)
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item(var(string1) tt(>) var(string2))(
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true if var(string1) comes after var(string2)
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based on ASCII value of their characters.
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)
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item(var(exp1) tt(-eq) var(exp2))(
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true if var(exp1) is numerically equal to var(exp2).
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)
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item(var(exp1) tt(-ne) var(exp2))(
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true if var(exp1) is numerically not equal to var(exp2).
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)
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item(var(exp1) tt(-lt) var(exp2))(
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true if var(exp1) is numerically less than var(exp2).
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)
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item(var(exp1) tt(-gt) var(exp2))(
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true if var(exp1) is numerically greater than var(exp2).
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)
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item(var(exp1) tt(-le) var(exp2))(
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true if var(exp1) is numerically less than or equal to var(exp2).
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)
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item(var(exp1) tt(-ge) var(exp2))(
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true if var(exp1) is numerically greater than or equal to var(exp2).
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)
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item(tt(LPAR()) var(exp) tt(RPAR()))(
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true if var(exp) is true.
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)
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item(tt(!) var(exp))(
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true if var(exp) is false.
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)
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item(var(exp1) tt(&&) var(exp2))(
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true if var(exp1) and var(exp2) are both true.
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)
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item(var(exp1) tt(||) var(exp2))(
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true if either var(exp1) or var(exp2) is true.
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)
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enditem()
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In each of the above expressions, if
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var(file) is of the form `tt(/dev/fd/)var(n)',
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where var(n) is an integer,
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then the test applied to the open file whose
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descriptor number is var(n),
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even if the underlying system does not support
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the tt(/dev/fd) directory.
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