1expr(1) User Commands expr(1)
2
6 expr - evaluate arguments as an expression
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9 /usr/bin/expr argument...
10 /usr/xpg4/bin/expr argument...
13 /usr/xpg6/bin/expr argument...
16
19 /usr/bin/expr, /usr/xpg4/bin/expr
20 The expr utility evaluates the expression and writes the result to
21 standard output. The character 0 is written to indicate a zero value
22 and nothing is written to indicate a null string.
23 /usr/xpg6/bin/expr
25 The expr utility evaluates the expression and writes the result to
26 standard output followed by a NEWLINE. If there is no result from expr
27 processing, a NEWLINE is written to standard output.
28
30 The argument operand is evaluated as an expression. Terms of the
31 expression must be separated by blanks. Characters special to the shell
32 must be escaped (see sh(1)). Strings containing blanks or other special
33 characters should be quoted. The length of the expression is limited to
34 LINE_MAX (2048 characters).
35 The operators and keywords are listed below. The list is in order of
38 increasing precedence, with equal precedence operators grouped within
39 {} symbols. All of the operators are left-associative.
40 expr \| expr
42 Returns the evaluation of the first expr if it is neither NULL nor
44 0; otherwise, returns the evaluation of the second expr if it is
45 not NULL; otherwise, 0.
46 expr \& expr
49 Returns the first expr if neither expr is NULL or 0, otherwise
51 returns 0.
52 expr{ =, \>, \>=, \<, \<=, !=} expr
55 Returns the result of an integer comparison if both arguments are
57 integers, otherwise returns the result of a string comparison using
58 the locale-specific coalition sequence. The result of each compari‐
59 son will be 1 if the specified relationship is TRUE, 0 if the rela‐
60 tionship is FALSE.
61 expr { +, − } expr
64 Addition or subtraction of integer-valued arguments.
66 expr { \*, /, %} expr
69 Multiplication, division, or remainder of the integer-valued argu‐
71 ments.
72 expr : expr
75 The matching operator : (colon) compares the first argument with
77 the second argument, which must be an internationalized basic regu‐
78 lar expression (BRE), except that all patterns are anchored to the
79 beginning of the string. That is, only sequences starting at the
80 first character of a string are matched by the regular expression.
81 See regex(5) and NOTES. Normally, the /usr/bin/expr matching opera‐
82 tor returns the number of bytes matched and the /usr/xpg4/bin/expr
83 matching operator returns the number of characters matched (0 on
84 failure). If the second argument contains at least one BRE sub-
85 expression [\(...\)], the matching operator returns the string cor‐
86 responding to \1.
87 integer
90 An argument consisting only of an (optional) unary minus followed
92 by digits.
93 string
96 A string argument that cannot be identified as an integer argument
98 or as one of the expression operator symbols.
99 Compatibility Operators (x86 only)
102 The following operators are included for compatibility with INTERACTIVE
103 UNIX System only and are not intended to be used by non- INTERACTIVE
104 UNIX System scripts:
105 index string character-list
107 Report the first position in which any one of the bytes in charac‐
109 ter-list matches a byte in string.
110 length string
113 Return the length (that is, the number of bytes) of string.
115 substr string integer-1 integer-2
118 Extract the substring of string starting at position integer-1 and
120 of length integer-2 bytes. If integer-1 has a value greater than
121 the number of bytes in string, expr returns a null string. If you
122 try to extract more bytes than there are in string, expr returns
123 all the remaining bytes from string. Results are unspecified if
124 either integer-1 or integer-2 is a negative value.
125
128 Example 1 Adding an integer to a shell variable
129 Add 1 to the shell variable a:
132 example$ a=`expr $a + 1`
135 Example 2 Returning a path name segment
139 The following example emulates basename(1), returning the last segment
142 of the path name $a. For $a equal to either /usr/abc/file or just file,
143 the example returns file. (Watch out for / alone as an argument: expr
144 takes it as the division operator. See NOTES below.)
145 example$ expr $a : '.*/\(.*\)' \| $a
148 Example 3 Using // characters to simplify the expression
152 Here is a better version of the previous example. The addition of the
155 // characters eliminates any ambiguity about the division operator and
156 simplifies the whole expression.
157 example$ expr //$a : '.*/\(.*\)'
160 /usr/bin/expr
164 Example 4 Returning the number of bytes in a variable
165 example$ expr "$VAR" : '.*'
167 /usr/xpg4/bin/expr
171 Example 5 Returning the number of characters in a variable
172 example$ expr "$VAR" : '.*'
174
178 See environ(5) for descriptions of the following environment variables
179 that affect the execution of expr: LANG, LC_ALL, LC_COLLATE, LC_CTYPE,
180 LC_MESSAGES, and NLSPATH.
181
183 As a side effect of expression evaluation, expr returns the following
184 exit values:
185 0 If the expression is neither NULL nor 0.
187 1 If the expression is either NULL or 0.
190 2 For invalid expressions.
193 >2 An error occurred.
196
199 See attributes(5) for descriptions of the following attributes:
200 ┌─────────────────────────────┬─────────────────────────────┐
205 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
206 ├─────────────────────────────┼─────────────────────────────┤
207 │Availability │SUNWcsu │
208 ├─────────────────────────────┼─────────────────────────────┤
209 │CSI │enabled │
210 ├─────────────────────────────┼─────────────────────────────┤
211 │Interface Stability │Standard │
212 └─────────────────────────────┴─────────────────────────────┘
213
215 basename(1), ed(1), sh(1), Intro(3), attributes(5), environ(5),
216 regex(5), standards(5)
217
219 syntax error Operator and operand errors.
220 non-numeric argument Arithmetic is attempted on such a string.
223
226 After argument processing by the shell, expr cannot tell the difference
227 between an operator and an operand except by the value. If $a is an =,
228 the command:
229 example$ expr $a = '='
231 looks like:
236 example$ expr = = =
238 as the arguments are passed to expr (and they are all taken as the =
243 operator). The following works:
244 example$ expr X$a = X=
246 Regular Expressions
250 Unlike some previous versions, expr uses Internationalized Basic Regu‐
251 lar Expressions for all system-provided locales. Internationalized Reg‐
252 ular Expressions are explained on the regex(5) manual page.
253SunOS 5.11 29 Aug 2003 expr(1)