


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)




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   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 counterparts:

           fread(p, size, n, stream)   PerlIO_read(perlio, buf, numbytes)
           fwrite(p, size, n, stream)  PerlIO_write(perlio, buf, numbytes)

           fputs(s, stream)            PerlIO_puts(perlio, s)

       There is no equivalent to "fgets"; one should use
       "sv_gets" instead:

           fgets(s, n, stream)         sv_gets(sv, perlio, append)

   File Positioning
           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)



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       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 as 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)
           Poison(dst, n, t)           equal to PoisonFree(dst, n, t)

   Character Class Tests
       There are two types of character class tests that Perl
       implements: one type deals in "char"s and are thus not
       Unicode aware (and hence deprecated unless you know you
       should use them) and the other type deal in "UV"s and know
       about Unicode properties. In the following table, "c" is a
       "char", and "u" is a Unicode codepoint.

           Instead Of:                 Use:            But better use:

           isalnum(c)                  isALNUM(c)      isALNUM_uni(u)
           isalpha(c)                  isALPHA(c)      isALPHA_uni(u)
           iscntrl(c)                  isCNTRL(c)      isCNTRL_uni(u)
           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)



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


   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"




















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