The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


atol - convert a string to long integer


#include <stdlib.h>

long int atol(const char *str);


The call atol(str) is equivalent to:

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

except that the handling of errors may differ. If the value cannot be represented, the behaviour is undefined.


The atol() function returns the converted value if the value can be represented.


No errors are defined.




The atol() function is subsumed by strtol() but is retained because it is used extensively in existing code. If the number is not known to be in range, strtol() should be used because atol() is not required to perform any error checking.




strtol(), <stdlib.h>.


Derived from Issue 1 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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