Hello Andrew, On 4/7/20 6:06 AM, Andrew Micallef wrote: > Hi Michael, > > I'd like to suggest an edit to the description of `strcmp` in the standard C library man page. > I found this description to be kind of confusing, and think the language could be a bit more > straight forward. > At present the description reads as follows: > > The strcmp() function compares the two strings s1 and s2. The locale > is not taken into account (for a locale-aware comparison, see > strcoll(3)<http://man7.org/linux/man-pages/man3/strcoll.3.html>). > It returns an integer less than, equal to, or greater > than zero if s1 is found, respectively, to be less than, to match, or > be greater than s2. > > I am suggesting the following edits: > > The strcmp() function compares the two strings s1 and s2. The locale > is not taken into account (for a locale-aware comparison, see > strcoll(3)<http://man7.org/linux/man-pages/man3/strcoll.3.html>). > It returns an integer, which is 0 if the strings > match. Otherwise, a negative integer indicates s1 is less than s2, > while a positive integer indicates s1 is greater than s2. As Ponnuvel points out, the text pretty much matches POSIX. It is terse, and clear. But also not so easy to parse, at least for some of us. Furthermore, the text is essentially repeated twice in the page, once in DESCRIPTION and then again in RETURN VALUE. Let's fix one of those in the direction you suggest. Also, I like Walter's suggestion of mentioning the arithmetic difference. How about this: DESCRIPTION The strcmp() function compares the two strings s1 and s2. The locale is not taken into account (for a locale-aware comparison, see strcoll(3)). The comparison is done using unsigned charac‐ ters. * strcmp() returns an integer indicating the result of the compari‐ * son, as follows: * * · 0, if the s1 and s2 are equal; * * · a negative value if s1 is less than s2; * * · a positive value if s1 is greater than s2; The strncmp() function is similar, except it compares only the first (at most) n bytes of s1 and s2. RETURN VALUE The strcmp() and strncmp() functions return an integer less than, equal to, or greater than zero if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match, or be greater than s2. ... NOTES * POSIX.1 specifies only that: * The sign of a non-zero return value shall be determined by * the sign of the difference between the values of the first * pair of bytes (both interpreted as type unsigned char) that * differ in the strings being compared. * * In glibc, as in most other implementations, the return value is * the arithmetic result of subtracting the last compared character * in s2 from the last compared character in s1. (If the two charac‐ * ters are equal, this difference is 0.) Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
