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User Commands expr(1)
NAME
expr - evaluate arguments as an expression
SYNOPSIS
/usr/bin/expr argument...
/usr/xpg4/bin/expr argument...
/usr/xpg6/bin/expr argument...
DESCRIPTION
/usr/bin/expr, /usr/xpg4/bin/expr
The expr utility evaluates the expression and writes the
result to standard output. The character 0 is written to
indicate a zero value and nothing is written to indicate a
null string.
/usr/xpg6/bin/expr
The expr utility evaluates the expression and writes the
result to standard output followed by a NEWLINE. If there is
no result from expr processing, a NEWLINE is written to
standard output.
OPERANDS
The argument operand is evaluated as an expression. Terms of
the expression must be separated by blanks. Characters spe-
cial to the shell must be escaped (see sh(1)). Strings con-
taining blanks or other special characters should be quoted.
The length of the expression is limited to LINE_MAX (2048
characters).
The operators and keywords are listed below. The list is in
order of increasing precedence, with equal precedence opera-
tors grouped within {} symbols. All of the operators are
left-associative.
expr \| expr
Returns the evaluation of the first expr if it is nei-
ther NULL nor 0; otherwise, returns the evaluation of
the second expr if it is not NULL; otherwise, 0.
expr \& expr
Returns the first expr if neither expr is NULL or 0,
otherwise returns 0.
SunOS 5.10 Last change: 29 Aug 2003 1
User Commands expr(1)
expr{ =, \>, \>=, \<, \<=, !=} expr
Returns the result of an integer comparison if both
arguments are integers, otherwise returns the result of
a string comparison using the locale-specific coalition
sequence. The result of each comparison will be 1 if the
specified relationship is TRUE, 0 if the relationship is
FALSE.
expr { +, - } expr
Addition or subtraction of integer-valued arguments.
expr { \*, /, %} expr
Multiplication, division, or remainder of the integer-
valued arguments.
expr : expr
The matching operator : (colon) compares the first argu-
ment with the second argument, which must be an interna-
tionalized basic regular expression (BRE), except that
all patterns are anchored to the beginning of the
string. That is, only sequences starting at the first
character of a string are matched by the regular expres-
sion. See regex(5) and NOTES. Normally, the
/usr/bin/expr matching operator returns the number of
bytes matched and the /usr/xpg4/bin/expr matching opera-
tor returns the number of characters matched (0 on
failure). If the second argument contains at least one
BRE sub-expression [\(...\)], the matching operator
returns the string corresponding to \1.
integer
An argument consisting only of an (optional) unary minus
followed by digits.
string
A string argument that cannot be identified as an
SunOS 5.10 Last change: 29 Aug 2003 2
User Commands expr(1)
integer argument or as one of the expression operator
symbols.
Compatibility Operators (x86 only)
The following operators are included for compatibility with
INTERACTIVE UNIX System only and are not intended to be used
by non- INTERACTIVE UNIX System scripts:
index string character-list
Report the first position in which any one of the bytes
in character-list matches a byte in string.
length string
Return the length (that is, the number of bytes) of
string.
substr string integer-1 integer-2
Extract the substring of string starting at position
integer-1 and of length integer-2 bytes. If integer-1
has a value greater than the number of bytes in string,
expr returns a null string. If you try to extract more
bytes than there are in string, expr returns all the
remaining bytes from string. Results are unspecified if
either integer-1 or integer-2 is a negative value.
EXAMPLES
Example 1: Adding an integer to a shell variable
Add 1 to the shell variable a:
example$ a=`expr $a + 1`
Example 2: Returning a path name segment
The following example emulates basename(1), returning the
last segment of the path name $a. For $a equal to either
/usr/abc/file or just file, the example returns file. (Watch
out for / alone as an argument: expr takes it as the divi-
sion operator. See NOTES below.)
SunOS 5.10 Last change: 29 Aug 2003 3
User Commands expr(1)
example$ expr $a : '.*/\(.*\)' \| $a
Example 3: Using // characters to simplify the expression
Here is a better version of the previous example. The addi-
tion of the // characters eliminates any ambiguity about the
division operator and simplifies the whole expression.
example$ expr //$a : '.*/\(.*\)'
/usr/bin/expr
Example 4: Returning the number of bytes in a variable
example$ expr "$VAR" : '.*'
/usr/xpg4/bin/expr
Example 5: Returning the number of characters in a variable
example$ expr "$VAR" : '.*'
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of expr: LANG, LC_ALL,
LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.
EXIT STATUS
As a side effect of expression evaluation, expr returns the
following exit values:
0 If the expression is neither NULL nor 0.
1 If the expression is either NULL or 0.
2 For invalid expressions.
>2 An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
SunOS 5.10 Last change: 29 Aug 2003 4
User Commands expr(1)
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | enabled |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
basename(1), ed(1), sh(1), Intro(3), attributes(5),
environ(5), regex(5), standards(5)
DIAGNOSTICS
syntax error Operator and operand errors.
non-numeric argument Arithmetic is attempted on such a
string.
NOTES
After argument processing by the shell, expr cannot tell the
difference between an operator and an operand except by the
value. If $a is an =, the command:
example$ expr $a = '='
looks like:
example$ expr = = =
as the arguments are passed to expr (and they are all taken
as the = operator). The following works:
example$ expr X$a = X=
Regular Expressions
Unlike some previous versions, expr uses Internationalized
Basic Regular Expressions for all system-provided locales.
Internationalized Regular Expressions are explained on the
regex(5) manual page.
SunOS 5.10 Last change: 29 Aug 2003 5
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This page was generated on Wed Sep 12 11:24:39 GMT 2007
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