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diff --git a/coreutils-5.3.0-bin/man/cat1p/expr.1p.txt b/coreutils-5.3.0-bin/man/cat1p/expr.1p.txt new file mode 100644 index 0000000..3c00ecb --- /dev/null +++ b/coreutils-5.3.0-bin/man/cat1p/expr.1p.txt @@ -0,0 +1,299 @@ +expr(P) expr(P) + + + + + +NAME + expr - evaluate arguments as an expression + +SYNOPSIS + expr operand + +DESCRIPTION + The expr utility shall evaluate an expression and write + the result to standard output. + +OPTIONS + None. + +OPERANDS + The single expression evaluated by expr shall be formed + from the operands, as described in the EXTENDED DESCRIP- + TION section. The application shall ensure that each of + the expression operator symbols: + + + ( ) | & = > >= < <= != + - * / % : + + and the symbols integer and string in the table are pro- + vided as separate arguments to expr. + +STDIN + Not used. + +INPUT FILES + None. + +ENVIRONMENT VARIABLES + The following environment variables shall affect the + execution of expr: + + LANG Provide a default value for the internationaliza- + tion variables that are unset or null. (See the + Base Definitions volume of IEEE Std 1003.1-2001, + Section 8.2, Internationalization Variables for + the precedence of internationalization variables + used to determine the values of locale cate- + gories.) + + LC_ALL If set to a non-empty string value, override the + values of all the other internationalization + variables. + + LC_COLLATE + + Determine the locale for the behavior of ranges, + equivalence classes, and multi-character collat- + ing elements within regular expressions and by + the string comparison operators. + + LC_CTYPE + Determine the locale for the interpretation of + sequences of bytes of text data as characters + (for example, single-byte as opposed to multi- + byte characters in arguments) and the behavior of + character classes within regular expressions. + + LC_MESSAGES + Determine the locale that should be used to + affect the format and contents of diagnostic + messages written to standard error. + + NLSPATH + Determine the location of message catalogs for + the processing of LC_MESSAGES . + + +ASYNCHRONOUS EVENTS + Default. + +STDOUT + The expr utility shall evaluate the expression and write + the result, followed by a <newline>, to standard output. + +STDERR + The standard error shall be used only for diagnostic + messages. + +OUTPUT FILES + None. + +EXTENDED DESCRIPTION + The formation of the expression to be evaluated is shown + in the following table. The symbols expr, expr1, and + expr2 represent expressions formed from integer and + string symbols and the expression operator symbols (all + separate arguments) by recursive application of the con- + structs described in the table. The expressions are + listed in order of increasing precedence, with equal- + precedence operators grouped between horizontal lines. + All of the operators shall be left-associative. +Expression Description +expr1 | expr2 Returns the evaluation of expr1 if it is neither null nor zero; otherwise, returns the evaluation of expr2 if it is not null; otherwise, zero. +expr1 & expr2 Returns the evaluation of expr1 if neither expression evaluates to null or zero; otherwise, returns zero. + Returns the result of a decimal integer comparison if both arguments are integers; otherwise, returns the result of a string comparison using the locale-specific collation sequence. The result of each comparison is 1 if the specified relationship is true, or 0 if the relationship is false. +expr1 = expr2 Equal. +expr1 > expr2 Greater than. +expr1 >= expr2 Greater than or equal. +expr1 < expr2 Less than. +expr1 <= expr2 Less than or equal. +expr1 != expr2 Not equal. +expr1 + expr2 Addition of decimal integer-valued arguments. +expr1 - expr2 Subtraction of decimal integer-valued arguments. +expr1 * expr2 Multiplication of decimal integer-valued arguments. +expr1 / expr2 Integer division of decimal integer-valued arguments, producing an integer result. +expr1 % expr2 Remainder of integer division of decimal integer-valued arguments. +expr1 : expr2 Matching expression; see below. +( expr ) Grouping symbols. Any expression can be placed within parentheses. Parentheses can be nested to a depth of {EXPR_NEST_MAX}. +integer An argument consisting only of an (optional) unary minus followed by digits. +string A string argument; see below. + + Matching Expression + The ':' matching operator shall compare the string + resulting from the evaluation of expr1 with the regular + expression pattern resulting from the evaluation of + expr2. Regular expression syntax shall be that defined + in the Base Definitions volume of IEEE Std 1003.1-2001, + Section 9.3, Basic Regular Expressions, 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 expression) and, + therefore, it is unspecified whether '^' is a special + character in that context. Usually, the matching opera- + tor shall return a string representing the number of + characters matched ( '0' on failure). Alternatively, if + the pattern contains at least one regular expression + subexpression "[\(...\)]" , the string corresponding to + "\1" shall be returned. + + String Operand + A string argument is an argument that cannot be identi- + fied as an integer argument or as one of the expression + operator symbols shown in the OPERANDS section. + + The use of string arguments length, substr, index, or + match produces unspecified results. + +EXIT STATUS + The following exit values shall be returned: + + 0 The expression evaluates to neither null nor + zero. + + 1 The expression evaluates to null or zero. + + 2 Invalid expression. + + >2 An error occurred. + + +CONSEQUENCES OF ERRORS + Default. + + The following sections are informative. + +APPLICATION USAGE + After argument processing by the shell, expr is not + required to be able to tell the difference between an + operator and an operand except by the value. If "$a" is + '=' , the command: + + + expr $a = '=' + + looks like: + + + expr = = = + + as the arguments are passed to expr (and they all may be + taken as the '=' operator). The following works reli- + ably: + + + expr X$a = X= + + Also note that this volume of IEEE Std 1003.1-2001 per- + mits implementations to extend utilities. The expr util- + ity permits the integer arguments to be preceded with a + unary minus. This means that an integer argument could + look like an option. Therefore, the conforming applica- + tion must employ the "--" construct of Guideline 10 of + the Base Definitions volume of IEEE Std 1003.1-2001, + Section 12.2, Utility Syntax Guidelines to protect its + operands if there is any chance the first operand might + be a negative integer (or any string with a leading + minus). + +EXAMPLES + The expr utility has a rather difficult syntax: + + Many of the operators are also shell control + operators or reserved words, so they have to be + escaped on the command line. + + Each part of the expression is composed of sepa- + rate arguments, so liberal usage of <blank>s is + required. For example: + Invalid Valid + + expr 1+2 expr 1 + 2 + expr "1 + 2" expr 1 + 2 + expr 1 + (2 * 3) expr 1 + \( 2 \* 3 \) + + In many cases, the arithmetic and string features pro- + vided as part of the shell command language are easier + to use than their equivalents in expr. Newly written + scripts should avoid expr in favor of the new features + within the shell; see Parameters and Variables and + Arithmetic Expansion . + + The following command: + + + a=$(expr $a + 1) + + adds 1 to the variable a. + + The following command, for "$a" equal to either + /usr/abc/file or just file: + + + expr $a : '.*/\(.*\)' \| $a + + returns the last segment of a pathname (that is, file). + Applications should avoid the character '/' used alone + as an argument; expr may interpret it as the division + operator. + + The following command: + + + expr "//$a" : '.*/\(.*\)' + + is a better representation of the previous example. The + addition of the "//" characters eliminates any ambiguity + about the division operator and simplifies the whole + expression. Also note that pathnames may contain charac- + ters contained in the IFS variable and should be quoted + to avoid having "$a" expand into multiple arguments. + + The following command: + + + expr "$VAR" : '.*' + + returns the number of characters in VAR. + +RATIONALE + In an early proposal, EREs were used in the matching + expression syntax. This was changed to BREs to avoid + breaking historical applications. + + The use of a leading circumflex in the BRE is unspeci- + fied because many historical implementations have + treated it as a special character, despite their system + documentation. For example: + + + expr foo : ^foo expr ^foo : ^foo + + return 3 and 0, respectively, on those systems; their + documentation would imply the reverse. Thus, the anchor- + ing condition is left unspecified to avoid breaking his- + torical scripts relying on this undocumented feature. + +FUTURE DIRECTIONS + None. + +SEE ALSO + Parameters and Variables , Arithmetic Expansion + +COPYRIGHT + Portions of this text are reprinted and reproduced in + electronic form from IEEE Std 1003.1, 2003 Edition, + Standard for Information Technology -- Portable Operat- + ing System Interface (POSIX), The Open Group Base Speci- + fications Issue 6, Copyright (C) 2001-2003 by the Insti- + tute of Electrical and Electronics Engineers, Inc and + The Open Group. In the event of any discrepancy between + this version and the original IEEE and The Open Group + Standard, the original IEEE and The Open Group Standard + is the referee document. The original Standard can be + obtained online at http://www.open- + group.org/unix/online.html . + + + +POSIX 2003 expr(P) |