3 perlclib - Internal replacements for standard C library functions
7 One thing Perl porters should note is that F<perl> doesn't tend to use that
8 much of the C standard library internally; you'll see very little use of,
9 for example, the F<ctype.h> functions in there. This is because Perl
10 tends to reimplement or abstract standard library functions, so that we
11 know exactly how they're going to operate.
13 This is a reference card for people who are familiar with the C library
14 and who want to do things the Perl way; to tell them which functions
15 they ought to use instead of the more normal C functions.
19 In the following tables:
41 C<sv>, C<av>, C<hv>, etc. represent variables of their respective types.
43 =head2 File Operations
45 Instead of the F<stdio.h> functions, you should use the Perl abstraction
46 layer. Instead of C<FILE*> types, you need to be handling C<PerlIO*>
47 types. Don't forget that with the new PerlIO layered I/O abstraction
48 C<FILE*> types may not even be available. See also the C<perlapio>
49 documentation for more information about the following functions:
54 stdout PerlIO_stdout()
55 stderr PerlIO_stderr()
57 fopen(fn, mode) PerlIO_open(fn, mode)
58 freopen(fn, mode, stream) PerlIO_reopen(fn, mode, perlio) (Deprecated)
59 fflush(stream) PerlIO_flush(perlio)
60 fclose(stream) PerlIO_close(perlio)
62 =head2 File Input and Output
66 fprintf(stream, fmt, ...) PerlIO_printf(perlio, fmt, ...)
68 [f]getc(stream) PerlIO_getc(perlio)
69 [f]putc(stream, n) PerlIO_putc(perlio, n)
70 ungetc(n, stream) PerlIO_ungetc(perlio, n)
72 Note that the PerlIO equivalents of C<fread> and C<fwrite> are slightly
73 different from their C library counterparts:
75 fread(p, size, n, stream) PerlIO_read(perlio, buf, numbytes)
76 fwrite(p, size, n, stream) PerlIO_write(perlio, buf, numbytes)
78 fputs(s, stream) PerlIO_puts(perlio, s)
80 There is no equivalent to C<fgets>; one should use C<sv_gets> instead:
82 fgets(s, n, stream) sv_gets(sv, perlio, append)
84 =head2 File Positioning
88 feof(stream) PerlIO_eof(perlio)
89 fseek(stream, n, whence) PerlIO_seek(perlio, n, whence)
90 rewind(stream) PerlIO_rewind(perlio)
92 fgetpos(stream, p) PerlIO_getpos(perlio, sv)
93 fsetpos(stream, p) PerlIO_setpos(perlio, sv)
95 ferror(stream) PerlIO_error(perlio)
96 clearerr(stream) PerlIO_clearerr(perlio)
98 =head2 Memory Management and String Handling
102 t* p = malloc(n) Newx(id, p, n, t)
103 t* p = calloc(n, s) Newxz(id, p, n, t)
104 p = realloc(p, n) Renew(p, n, t)
105 memcpy(dst, src, n) Copy(src, dst, n, t)
106 memmove(dst, src, n) Move(src, dst, n, t)
107 memcpy/*(struct foo *) StructCopy(src, dst, t)
108 memset(dst, 0, n * sizeof(t)) Zero(dst, n, t)
109 memzero(dst, 0) Zero(dst, n, char)
113 strndup(p, n) savepvn(p, n) (Hey, strndup doesn't exist!)
115 strstr(big, little) instr(big, little)
116 strcmp(s1, s2) strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
117 strncmp(s1, s2, n) strnNE(s1, s2, n) / strnEQ(s1, s2, n)
119 Notice the different order of arguments to C<Copy> and C<Move> than used
120 in C<memcpy> and C<memmove>.
122 Most of the time, though, you'll want to be dealing with SVs internally
123 instead of raw C<char *> strings:
126 strcpy(dt, src) sv_setpv(sv, s)
127 strncpy(dt, src, n) sv_setpvn(sv, s, n)
128 strcat(dt, src) sv_catpv(sv, s)
129 strncat(dt, src) sv_catpvn(sv, s)
130 sprintf(s, fmt, ...) sv_setpvf(sv, fmt, ...)
132 Note also the existence of C<sv_catpvf> and C<sv_vcatpvfn>, combining
133 concatenation with formatting.
135 Sometimes instead of zeroing the allocated heap by using Newxz() you
136 should consider "poisoning" the data. This means writing a bit
137 pattern into it that should be illegal as pointers (and floating point
138 numbers), and also hopefully surprising enough as integers, so that
139 any code attempting to use the data without forethought will break
140 sooner rather than later. Poisoning can be done using the Poison()
141 macros, which have similar arguments as Zero():
143 PoisonWith(dst, n, t, b) scribble memory with byte b
144 PoisonNew(dst, n, t) equal to PoisonWith(dst, n, t, 0xAB)
145 PoisonFree(dst, n, t) equal to PoisonWith(dst, n, t, 0xEF)
146 Poison(dst, n, t) equal to PoisonFree(dst, n, t)
148 =head2 Character Class Tests
150 There are two types of character class tests that Perl implements: one
151 type deals in C<char>s and are thus B<not> Unicode aware (and hence
152 deprecated unless you B<know> you should use them) and the other type
153 deal in C<UV>s and know about Unicode properties. In the following
154 table, C<c> is a C<char>, and C<u> is a Unicode codepoint.
156 Instead Of: Use: But better use:
158 isalnum(c) isALNUM(c) isALNUM_uni(u)
159 isalpha(c) isALPHA(c) isALPHA_uni(u)
160 iscntrl(c) isCNTRL(c) isCNTRL_uni(u)
161 isdigit(c) isDIGIT(c) isDIGIT_uni(u)
162 isgraph(c) isGRAPH(c) isGRAPH_uni(u)
163 islower(c) isLOWER(c) isLOWER_uni(u)
164 isprint(c) isPRINT(c) isPRINT_uni(u)
165 ispunct(c) isPUNCT(c) isPUNCT_uni(u)
166 isspace(c) isSPACE(c) isSPACE_uni(u)
167 isupper(c) isUPPER(c) isUPPER_uni(u)
168 isxdigit(c) isXDIGIT(c) isXDIGIT_uni(u)
170 tolower(c) toLOWER(c) toLOWER_uni(u)
171 toupper(c) toUPPER(c) toUPPER_uni(u)
173 =head2 F<stdlib.h> functions
179 strtod(s, *p) Nothing. Just don't use it.
180 strtol(s, *p, n) Strtol(s, *p, n)
181 strtoul(s, *p, n) Strtoul(s, *p, n)
183 Notice also the C<grok_bin>, C<grok_hex>, and C<grok_oct> functions in
184 F<numeric.c> for converting strings representing numbers in the respective
187 In theory C<Strtol> and C<Strtoul> may not be defined if the machine perl is
188 built on doesn't actually have strtol and strtoul. But as those 2
189 functions are part of the 1989 ANSI C spec we suspect you'll find them
192 int rand() double Drand01()
193 srand(n) { seedDrand01((Rand_seed_t)n);
194 PL_srand_called = TRUE; }
197 system(s) Don't. Look at pp_system or use my_popen
199 getenv(s) PerlEnv_getenv(s)
200 setenv(s, val) my_putenv(s, val)
202 =head2 Miscellaneous functions
204 You should not even B<want> to use F<setjmp.h> functions, but if you
205 think you do, use the C<JMPENV> stack in F<scope.h> instead.
207 For C<signal>/C<sigaction>, use C<rsignal(signo, handler)>.
211 C<perlapi>, C<perlapio>, C<perlguts>