ref: 8caf4d3bcbabe28d34556ea6b5542b491ea43e27
dir: /sys/man/2/atof/
.TH ATOF 2 .SH NAME atof, atoi, atol, atoll, charstod, strtod, strtol, strtoll, strtoul, strtoull \- convert text to numbers .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .nf .ta \w'\fLdouble 'u .B double atof(char *nptr) .PP .B int atoi(char *nptr) .PP .B long atol(char *nptr) .PP .B vlong atoll(char *nptr) .PP .B double charstod(int (*f)(void *), void *a) .PP .B double strtod(char *nptr, char **rptr) .PP .B long strtol(char *nptr, char **rptr, int base) .PP .B vlong strtoll(char *nptr, char **rptr, int base) .PP .B ulong strtoul(char *nptr, char **rptr, int base) .PP .B uvlong strtoull(char *nptr, char **rptr, int base) .fi .SH DESCRIPTION .IR Atof , .IR atoi , .IR atol , and .I atoll convert a string pointed to by .I nptr to floating, integer, long integer, and long long integer .RB ( vlong ) representation respectively. The first unrecognized character ends the string. Leading C escapes are understood, as in .I strtol with .I base zero (described below). .PP .I Atof recognizes an optional string of tabs and spaces, then an optional sign, then a string of digits optionally containing a decimal point, then an optional .L e or .L E followed by an optionally signed integer. .PP .I Atoi and .I atol recognize an optional string of tabs and spaces, then an optional sign, then a string of decimal digits. .PP .IR Strtod , .IR strtol , .IR strtoll , .IR strtoul , and .I strtoull behave similarly to .I atof and .I atol and, if .I rptr is not zero, set .I *rptr to point to the input character immediately after the string converted. .PP .IR Strtol , .IR strtoll , .IR strtoul , and .IR strtoull interpret the digit string in the specified .IR base , from 2 to 36, each digit being less than the base. Digits with value over 9 are represented by letters, a-z or A-Z. If .I base is 0, the input is interpreted as an integral constant in the style of C (with no suffixed type indicators): numbers are octal if they begin with .LR 0 , hexadecimal if they begin with .L 0x or .LR 0X , otherwise decimal. .PP .I Charstod interprets floating point numbers in the manner of .IR atof , but gets successive characters by calling .BR (*\fIf\fP)(a) . The last call to .I f terminates the scan, so it must have returned a character that is not a legal continuation of a number. Therefore, it may be necessary to back up the input stream one character after calling .IR charstod . .SH SOURCE .B /sys/src/libc/port .SH SEE ALSO .IR fscanf (2) .SH DIAGNOSTICS Zero is returned if the beginning of the input string is not interpretable as a number; even in this case, .I rptr will be updated. .SH BUGS .I Atoi, .I atol, and .I atoll accept octal and hexadecimal numbers in the style of C, contrary to the ANSI specification.