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

This is a reference card for people who are familiar with the C libraryand who want to do things the Perl way; to tell them which functionsthey 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 abstractionlayer. 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 perlapiodocumentation 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 slightlydifferent 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 usedin memcpy and memmove.

Most of the time, though, you'll want to be dealing with SVs internallyinstead 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, combiningconcatenation with formatting.

Sometimes instead of zeroing the allocated heap by using Newxz() youshould consider "poisoning" the data. This means writing a bitpattern into it that should be illegal as pointers (and floating pointnumbers), and also hopefully surprising enough as integers, so thatany code attempting to use the data without forethought will breaksooner 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: onetype deals in chars and are thus not Unicode aware (and hencedeprecated unless you know you should use them) and the other typedeal in UVs and know about Unicode properties. In the followingtable, 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 innumeric.c for converting strings representing numbers in the respectivebases into NVs.

In theory Strtol and Strtoul may not be defined if the machine perl isbuilt on doesn't actually have strtol and strtoul. But as those 2functions are part of the 1989 ANSI C spec we suspect you'll find themeverywhere 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 youthink you do, use the JMPENV stack in scope.h instead.

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

Internal replacements for standard C library functions

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