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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
       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)

       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)
           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)

   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 v5.16.2                                     2012-10-25                                      PERLCLIB(1)