STRTOL(3C)                           SysV                           STRTOL(3C)



NAME
     strtol, strtoul, atoi, atol - convert strings to numbers

SYNOPSIS
     #include <stdlib.h>

     long int strtol(nptr, endptr, base)
     const char *nptr;
     char **endptr;
     int base;

     unsigned long int strtoul(nptr, endptr, base)
     const char *nptr;
     char **endptr;
     int base;

     int atoi(nptr)
     const char *nptr;

     long int atol(nptr)
     const char *nptr;

DESCRIPTION
     strtol, and strtoul convert the initial portion of the string pointed to
     by nptr to double, long int, and unsigned long int representation,
     respectively.  These functions first decompose the input string into
     three parts:  an initial, possibly empty, sequence of white-space
     characters (as specified by isspace (ctype(3C))), or an integer or
     unsigned long integer represented in some radix determined by the value
     of base (in the case of strtol and strtoul, respectively), and a final
     string of one or more unrecognized characters, including the terminating
     null character of the input string.  Then they attempt to convert the
     subject sequence to a floating-point number, an integer, or an unsigned
     integer, respectively, and return the result.

     The form of the subject sequence that strtol and strtoul expect depends
     upon the value of base.  If the value of base is zero, strtol and strtoul
     expect a subject sequence consisting of an integer constant, optionally
     preceded by a plus or minus sign, but not including an integer suffix.
     If the value of base is between 2 and 35, strtol and strtoul expect a
     subject sequence consisting of a sequence of letters and digits
     representing an integer with the radix specified by base, optionally
     preceded by a plus or minus sign, but not including an integer suffix.
     The letters from "a" (or "A") through "z" (or "Z") are ascribed the
     values 10 to 35; only letters whose ascribed values are less than that of
     base are permitted.  If the value of base is 16, the characters "0x" or
     "0X" may optionally precede the sequence of letters and digits, following
     the sign, if present.

     The subject sequence, in the case of strtol and strtoul, is defined as
     the longest initial subsequence of the input string, starting with the
     first non-white-space character, that is of the expected form.  The
     subject sequence contains no characters if the input string is empty or
     consists entirely of white space, or if the first non-white-space
     character is other than a sign or a permissible letter or digit.

     If the subject sequence has the form strtol and strtoul expect and the
     value of base is zero, the sequence of characters starting with the first
     digit is interpreted  as an integer constant.  If the subject sequence
     has the form strtol and strtoul expect and the value of base is between 2
     and 36, it is used as the base for conversion, ascribing to each letter

     its value as given above.  If the subject sequence begins with a minus
     sign, the value resulting from the conversion is negated.  A pointer to
     the final string is stored in the object pointed to by endptr, provided
     that endptr is not a null pointer.

     If the subject sequence is empty or does not have the form strtol, or
     strtoul expect, no conversion is done.  The value of nptr is stored in
     the object pointed to by endptr, provided that endptr is not a null
     pointer.

     atoi converts the initial portion of the string pointed to by nptr to int
     representation.  Except for the behavior on error, it is equivalent to

          (int)strtol(nptr, (char **)NULL, 10)

     If the value cannot be represented, the behavior is undefined.

     atol converts the initial portion of the string pointed to by nptr to
     long int representation.  Except for the behavior on error, it is
     equivalent to

          strtol(nptr, (char **)NULL, 10)

SEE ALSO
     ctype(3C), scanf(3S) setlocale(3C) <stdlib.h>

DIAGNOSTICS
     These functions return the converted value, if any.  If atoi, or atol
     result in a value that cannot be represented, their behavior is
     undefined.  If strtol, or strtoul could not convert the string pointed to
     by nptr, they return zero.  If the correct value is outside the range of
     representable values, strtol and strtoul set errno to ERANGE.  In this
     case, strtol returns LONG_MAX or LONG_MIN (according to the sign of the
     value) and strtoul returns ULONG_MAX.

ERRORS
     strtol fails if:

     [EINVAL]       The value of base is not supported

NOTE
     Parts of this discussion are adapted from ANS X3.159-1989.

BUGS
     atoi, and atol do not provide for overflow.  "