ref: 2c9e3861a54e22498fb2e3226defe4393b20b202
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.