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//proc/self/root/usr/share/doc/gawk-3.1.5/POSIX.STD
March 2001: It looks like the revised 1003.2 standard will actually follow the rules given below. Hallelujah! October 1998: The 1003.2 work has been at a stand-still for ages. Who knows if or when a new revision will actually happen... August 1995: Although the published 1003.2 standard contained the incorrect comparison rules of 11.2 draft as described below, no actual implementation of awk (that I know of) actually used those rules. A revision of the 1003.2 standard is in progress, and in the May 1995 draft, the rules were fixed (based on my submissions for interpretation requests) to match the description given below. Thus, the next version of the standard will have a correct description of the comparison rules. June 1992: Right now, the numeric vs. string comparisons are screwed up in draft 11.2. What prompted me to check it out was the note in gnu.bug.utils which observed that gawk was doing the comparison $1 == "000" numerically. I think that we can agree that intuitively, this should be done as a string comparison. Version 2.13.2 of gawk follows the current POSIX draft. Following is how I (now) think this stuff should be done. 1. A numeric literal or the result of a numeric operation has the NUMERIC attribute. 2. A string literal or the result of a string operation has the STRING attribute. 3. Fields, getline input, FILENAME, ARGV elements, ENVIRON elements and the elements of an array created by split() that are numeric strings have the STRNUM attribute. Otherwise, they have the STRING attribute. Uninitialized variables also have the STRNUM attribute. 4. Attributes propagate across assignments, but are not changed by any use. (Although a use may cause the entity to acquire an additional value such that it has both a numeric and string value -- this leaves the attribute unchanged.) When two operands are compared, either string comparison or numeric comparison may be used, depending on the attributes of the operands, according to the following (symmetric) matrix: +---------------------------------------------- | STRING NUMERIC STRNUM --------+---------------------------------------------- | STRING | string string string | NUMERIC | string numeric numeric | STRNUM | string numeric numeric --------+---------------------------------------------- So, the following program should print all OKs. echo '0e2 0a 0 0b 0e2 0a 0 0b' | $AWK ' NR == 1 { num = 0 str = "0e2" print ++test ": " ( (str == "0e2") ? "OK" : "OOPS" ) print ++test ": " ( ("0e2" != 0) ? "OK" : "OOPS" ) print ++test ": " ( ("0" != $2) ? "OK" : "OOPS" ) print ++test ": " ( ("0e2" == $1) ? "OK" : "OOPS" ) print ++test ": " ( (0 == "0") ? "OK" : "OOPS" ) print ++test ": " ( (0 == num) ? "OK" : "OOPS" ) print ++test ": " ( (0 != $2) ? "OK" : "OOPS" ) print ++test ": " ( (0 == $1) ? "OK" : "OOPS" ) print ++test ": " ( ($1 != "0") ? "OK" : "OOPS" ) print ++test ": " ( ($1 == num) ? "OK" : "OOPS" ) print ++test ": " ( ($2 != 0) ? "OK" : "OOPS" ) print ++test ": " ( ($2 != $1) ? "OK" : "OOPS" ) print ++test ": " ( ($3 == 0) ? "OK" : "OOPS" ) print ++test ": " ( ($3 == $1) ? "OK" : "OOPS" ) print ++test ": " ( ($2 != $4) ? "OK" : "OOPS" ) # 15 } { a = "+2" b = 2 if (NR % 2) c = a + b print ++test ": " ( (a != b) ? "OK" : "OOPS" ) # 16 and 22 d = "2a" b = 2 if (NR % 2) c = d + b print ++test ": " ( (d != b) ? "OK" : "OOPS" ) print ++test ": " ( (d + 0 == b) ? "OK" : "OOPS" ) e = "2" print ++test ": " ( (e == b "") ? "OK" : "OOPS" ) a = "2.13" print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" ) a = "2.130000" print ++test ": " ( (a != 2.13) ? "OK" : "OOPS" ) if (NR == 2) { CONVFMT = "%.6f" print ++test ": " ( (a == 2.13) ? "OK" : "OOPS" ) } }'