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