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       stdlib.h - standard library definitions


       #include <stdlib.h>


       Some  of the functionality described on this reference page extends the
       ISO C standard. Applications shall define the appropriate feature  test
       macro  (see  the  System  Interfaces  volume  of  IEEE Std 1003.1-2001,
       Section 2.2, The Compilation Environment) to enable the  visibility  of
       these symbols in this header.

       The <stdlib.h> header shall define the following macros:

              Unsuccessful  termination  for  exit();  evaluates to a non-zero

              Successful termination for exit(); evaluates to 0.

       NULL   Null pointer.

              Maximum value returned by rand(); at least 32767.

              Integer expression whose value is the maximum number of bytes in
              a character specified by the current locale.

       The following data types shall be defined through typedef:

       div_t  Structure type returned by the div() function.

       ldiv_t Structure type returned by the ldiv() function.

              Structure type returned by the lldiv() function.

       size_t As described in <stddef.h> .

              As described in <stddef.h> .

       In  addition,  the following symbolic names and macros shall be defined
       as in <sys/wait.h>  ,  for  use  in  decoding  the  return  value  from


       The following shall be declared as functions and may also be defined as
       macros. Function prototypes shall be provided.

              void          _Exit(int);

              long          a64l(const char *);

              void          abort(void);
              int           abs(int);
              int           atexit(void (*)(void));
              double        atof(const char *);
              int           atoi(const char *);
              long          atol(const char *);
              long long     atoll(const char *);
              void         *bsearch(const void *, const void *, size_t, size_t,
                                int (*)(const void *, const void *));
              void         *calloc(size_t, size_t);
              div_t         div(int, int);

              double        drand48(void);
              char         *ecvt(double, int, int *restrict, int *restrict); (LEGACY )
              double        erand48(unsigned short[3]);

              void          exit(int);

              char         *fcvt(double, int, int *restrict, int *restrict); (LEGACY )

              void          free(void *);

              char         *gcvt(double, int, char *); (LEGACY )

              char         *getenv(const char *);

              int           getsubopt(char **, char *const *, char **);
              int           grantpt(int);
              char         *initstate(unsigned, char *, size_t);
              long          jrand48(unsigned short[3]);
              char         *l64a(long);

              long          labs(long);

              void          lcong48(unsigned short[7]);

              ldiv_t        ldiv(long, long);
              long long     llabs(long long);
              lldiv_t       lldiv(long long, long long);

              long          lrand48(void);

              void         *malloc(size_t);
              int           mblen(const char *, size_t);
              size_t        mbstowcs(wchar_t *restrict, const char *restrict, size_t);
              int           mbtowc(wchar_t *restrict, const char *restrict, size_t);

              char         *mktemp(char *); (LEGACY )
              int           mkstemp(char *);
              long          mrand48(void);
              long          nrand48(unsigned short[3]);

              int           posix_memalign(void **, size_t, size_t);

              int           posix_openpt(int);
              char         *ptsname(int);
              int           putenv(char *);

              void          qsort(void *, size_t, size_t, int (*)(const void *,
                                const void *));
              int           rand(void);

              int           rand_r(unsigned *);

              long          random(void);

              void         *realloc(void *, size_t);

              char         *realpath(const char *restrict, char *restrict);
              unsigned short seed48(unsigned short[3]);

              int           setenv(const char *, const char *, int);

              void          setkey(const char *);
              char         *setstate(const char *);

              void          srand(unsigned);

              void          srand48(long);
              void          srandom(unsigned);

              double        strtod(const char *restrict, char **restrict);
              float         strtof(const char *restrict, char **restrict);
              long          strtol(const char *restrict, char **restrict, int);
              long double   strtold(const char *restrict, char **restrict);
              long long     strtoll(const char *restrict, char **restrict, int);
              unsigned long strtoul(const char *restrict, char **restrict, int);
              unsigned long long
                            strtoull(const char *restrict, char **restrict, int);
              int           system(const char *);

              int           unlockpt(int);

              int           unsetenv(const char *);

              size_t        wcstombs(char *restrict, const wchar_t *restrict, size_t);
              int           wctomb(char *, wchar_t);

       Inclusion of the <stdlib.h> header may also make  visible  all  symbols
       from <stddef.h>, <limits.h>, <math.h>, and <sys/wait.h>.

       The following sections are informative.








       <limits.h> , <math.h> , <stddef.h> , <sys/types.h> , <sys/wait.h> , the
       System Interfaces  volume  of  IEEE Std 1003.1-2001,  _Exit(),  a64l(),
       abort(),  abs(),  atexit(), atof(), atoi(), atol(), atoll(), bsearch(),
       calloc(),  div(),  drand48(),  erand48(),  exit(),  free(),   getenv(),
       getsubopt(),   grantpt(),   initstate(),   jrand48(),  l64a(),  labs(),
       lcong48(), ldiv(),  llabs(),  lldiv(),  lrand48(),  malloc(),  mblen(),
       mbstowcs(),      mbtowc(),     mkstemp(),     mrand48(),     nrand48(),
       posix_memalign(),  ptsname(),  putenv(),  qsort(),  rand(),  realloc(),
       realpath(),   setstate(),   srand(),  srand48(),  srandom(),  strtod(),
       strtof(),  strtol(),  strtold(),  strtoll(),   strtoul(),   strtoull(),
       unlockpt(), wcstombs(), wctomb()


       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at .