Advanced Programming in the UNIX® Environment

ptg10805159

Section 2.5 Limits 37

2. Runtime limits not associated with a file or directory (thesysconffunction)


3. Runtime limits that areassociated with a file or a directory (thepathconfand
   fpathconffunctions)
   To further confuse things, if a particular runtime limit does not vary on a given system,
   it can be defined statically in a header.If it is not defined in a header,however,the
   application must call one of the threeconffunctions (which we describe shortly) to
   determine its value at runtime.

Minimum

Name Description acceptable value Typical value

CHAR_BIT bits in achar 88

CHAR_MAX max value ofchar (see later) 127

CHAR_MIN min value ofchar (see later) − 128

SCHAR_MAX max value ofsigned char 127 127

SCHAR_MIN min value ofsigned char − 127 − 128

UCHAR_MAX max value ofunsigned char 255 255

INT_MAX max value ofint 32,767 2,147,483,647

INT_MIN min value ofint −32,767 −2,147,483,648

UINT_MAX max value ofunsigned int 65,535 4,294,967,295

SHRT_MAX max value ofshort 32,767 32,767

SHRT_MIN min value ofshort −32,767 −32,768

USHRT_MAX max value ofunsigned short 65,535 65,535

LONG_MAX max value oflong 2,147,483,647 2,147,483,647

LONG_MIN min value oflong −2,147,483,647 −2,147,483,648

ULONG_MAX max value ofunsigned long 4,294,967,295 4,294,967,295

LLONG_MAX max value oflong long 9,223,372,036,854,775,807 9,223,372,036,854,775,807

LLONG_MIN min value oflong long −9,223,372,036,854,775,807 −9,223,372,036,854,775,808

ULLONG_MAX max value ofunsigned 18,446,744,073,709,551,615 18,446,744,073,709,551,615

long long

MB_LEN_MAX max number of bytes in a 16

multibyte character constant

Figure 2.6Sizes of integral values from<limits.h>

2.5.1 ISOCLimits

All of the compile-time limits defined by ISO C aredefined in the file<limits.h>(see

Figure2.6). These constants don’t change in a given system. The thirdcolumn in

Figure2.6 shows the minimum acceptable values from the ISO C standard. This allows

for a system with 16-bit integers using one’s-complement arithmetic. The fourth

column shows the values from a Linux system with 32-bit integers using two’s-

complement arithmetic. Note that none of the unsigned data types has a minimum

value, as this value must be 0 for an unsigned data type. On a 64-bit system, the values

forlonginteger maximums match the maximum values forlong longintegers.

One difference that we will encounter is whether a system provides signed or

unsigned character values. From the fourth column in Figure2.6, we see that this