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PERLCLIB(1)                                Perl Programmers Reference Guide                               PERLCLIB(1)



NAME
       perlclib - Internal replacements for standard C library functions

DESCRIPTION
       One thing Perl porters should note is that perl doesn't tend to use that much of the C standard library
       internally; you'll see very little use of, for example, the ctype.h functions in there. This is because Perl
       tends to reimplement or abstract standard library functions, so that we know exactly how they're going to
       operate.

       This is a reference card for people who are familiar with the C library and who want to do things the Perl
       way; to tell them which functions they ought to use instead of the more normal C functions.

   Conventions
       In the following tables:

       "t"
          is a type.

       "p"
          is a pointer.

       "n"
          is a number.

       "s"
          is a string.

       "sv", "av", "hv", etc. represent variables of their respective types.

   File Operations
       Instead of the stdio.h functions, you should use the Perl abstraction layer. Instead of "FILE*" types, you
       need to be handling "PerlIO*" types.  Don't forget that with the new PerlIO layered I/O abstraction "FILE*"
       types may not even be available. See also the "perlapio" documentation for more information about the
       following functions:

           Instead Of:                 Use:

           stdin                       PerlIO_stdin()
           stdout                      PerlIO_stdout()
           stderr                      PerlIO_stderr()

           fopen(fn, mode)             PerlIO_open(fn, mode)
           freopen(fn, mode, stream)   PerlIO_reopen(fn, mode, perlio) (Deprecated)
           fflush(stream)              PerlIO_flush(perlio)
           fclose(stream)              PerlIO_close(perlio)

   File Input and Output
           Instead Of:                 Use:

           fprintf(stream, fmt, ...)   PerlIO_printf(perlio, fmt, ...)

           [f]getc(stream)             PerlIO_getc(perlio)
           [f]putc(stream, n)          PerlIO_putc(perlio, n)
           ungetc(n, stream)           PerlIO_ungetc(perlio, n)

       Note that the PerlIO equivalents of "fread" and "fwrite" are slightly different from their C library

           Instead Of:                 Use:

           feof(stream)                PerlIO_eof(perlio)
           fseek(stream, n, whence)    PerlIO_seek(perlio, n, whence)
           rewind(stream)              PerlIO_rewind(perlio)

           fgetpos(stream, p)          PerlIO_getpos(perlio, sv)
           fsetpos(stream, p)          PerlIO_setpos(perlio, sv)

           ferror(stream)              PerlIO_error(perlio)
           clearerr(stream)            PerlIO_clearerr(perlio)

   Memory Management and String Handling
           Instead Of:                         Use:

           t* p = malloc(n)                    Newx(id, p, n, t)
           t* p = calloc(n, s)                 Newxz(id, p, n, t)
           p = realloc(p, n)                   Renew(p, n, t)
           memcpy(dst, src, n)                 Copy(src, dst, n, t)
           memmove(dst, src, n)                Move(src, dst, n, t)
           memcpy(dst, src, sizeof(t))         StructCopy(src, dst, t)
           memset(dst, 0, n * sizeof(t))       Zero(dst, n, t)
           memzero(dst, 0)                     Zero(dst, n, char)
           free(p)                             Safefree(p)

           strdup(p)                   savepv(p)
           strndup(p, n)               savepvn(p, n) (Hey, strndup doesn't exist!)

           strstr(big, little)         instr(big, little)
           strcmp(s1, s2)              strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
           strncmp(s1, s2, n)          strnNE(s1, s2, n) / strnEQ(s1, s2, n)

       Notice the different order of arguments to "Copy" and "Move" than used in "memcpy" and "memmove".

       Most of the time, though, you'll want to be dealing with SVs internally instead of raw "char *" strings:

           strlen(s)                   sv_len(sv)
           strcpy(dt, src)             sv_setpv(sv, s)
           strncpy(dt, src, n)         sv_setpvn(sv, s, n)
           strcat(dt, src)             sv_catpv(sv, s)
           strncat(dt, src)            sv_catpvn(sv, s)
           sprintf(s, fmt, ...)        sv_setpvf(sv, fmt, ...)

       Note also the existence of "sv_catpvf" and "sv_vcatpvfn", combining concatenation with formatting.

       Sometimes instead of zeroing the allocated heap by using Newxz() you should consider "poisoning" the data.
       This means writing a bit pattern into it that should be illegal as pointers (and floating point numbers), and
       also hopefully surprising enough as integers, so that any code attempting to use the data without forethought
       will break sooner rather than later.  Poisoning can be done using the Poison() macros, which have similar
       arguments to Zero():

           PoisonWith(dst, n, t, b)    scribble memory with byte b
           PoisonNew(dst, n, t)        equal to PoisonWith(dst, n, t, 0xAB)
           PoisonFree(dst, n, t)       equal to PoisonWith(dst, n, t, 0xEF)
           isdigit(c)                  isDIGIT(c)      isDIGIT_uni(u)
           isgraph(c)                  isGRAPH(c)      isGRAPH_uni(u)
           islower(c)                  isLOWER(c)      isLOWER_uni(u)
           isprint(c)                  isPRINT(c)      isPRINT_uni(u)
           ispunct(c)                  isPUNCT(c)      isPUNCT_uni(u)
           isspace(c)                  isSPACE(c)      isSPACE_uni(u)
           isupper(c)                  isUPPER(c)      isUPPER_uni(u)
           isxdigit(c)                 isXDIGIT(c)     isXDIGIT_uni(u)

           tolower(c)                  toLOWER(c)      toLOWER_uni(u)
           toupper(c)                  toUPPER(c)      toUPPER_uni(u)

   stdlib.h functions
           Instead Of:                 Use:

           atof(s)                     Atof(s)
           atol(s)                     Atol(s)
           strtod(s, &p)               Nothing.  Just don't use it.
           strtol(s, &p, n)            Strtol(s, &p, n)
           strtoul(s, &p, n)           Strtoul(s, &p, n)

       Notice also the "grok_bin", "grok_hex", and "grok_oct" functions in numeric.c for converting strings
       representing numbers in the respective bases into "NV"s.

       In theory "Strtol" and "Strtoul" may not be defined if the machine perl is built on doesn't actually have
       strtol and strtoul. But as those 2 functions are part of the 1989 ANSI C spec we suspect you'll find them
       everywhere by now.

           int rand()                  double Drand01()
           srand(n)                    { seedDrand01((Rand_seed_t)n);
                                         PL_srand_called = TRUE; }

           exit(n)                     my_exit(n)
           system(s)                   Don't. Look at pp_system or use my_popen

           getenv(s)                   PerlEnv_getenv(s)
           setenv(s, val)              my_putenv(s, val)

   Miscellaneous functions
       You should not even want to use setjmp.h functions, but if you think you do, use the "JMPENV" stack in scope.h
       instead.

       For "signal"/"sigaction", use "rsignal(signo, handler)".

SEE ALSO
       perlapi, perlapio, perlguts



perl v5.16.3                                          2013-03-04                                          PERLCLIB(1)