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.

       In the following tables:

          is a type.

          is a pointer.

          is a number.

          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)
           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(p, n, t)
           t* p = calloc(n, s)                 Newxz(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
       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.
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