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

6       perlclib - Internal replacements for standard C library functions
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DESCRIPTION

9       One thing Perl porters should note is that perl doesn't tend to use
10       that much of the C standard library internally; you'll see very little
11       use of, for example, the ctype.h functions in there. This is because
12       Perl tends to reimplement or abstract standard library functions, so
13       that we know exactly how they're going to operate.
14
15       This is a reference card for people who are familiar with the C library
16       and who want to do things the Perl way; to tell them which functions
17       they ought to use instead of the more normal C functions.
18
19   Conventions
20       In the following tables:
21
22       "t"
23          is a type.
24
25       "p"
26          is a pointer.
27
28       "n"
29          is a number.
30
31       "s"
32          is a string.
33
34       "sv", "av", "hv", etc. represent variables of their respective types.
35
36   File Operations
37       Instead of the stdio.h functions, you should use the Perl abstraction
38       layer. Instead of "FILE*" types, you need to be handling "PerlIO*"
39       types.  Don't forget that with the new PerlIO layered I/O abstraction
40       "FILE*" types may not even be available. See also the "perlapio"
41       documentation for more information about the following functions:
42
43           Instead Of:                 Use:
44
45           stdin                       PerlIO_stdin()
46           stdout                      PerlIO_stdout()
47           stderr                      PerlIO_stderr()
48
49           fopen(fn, mode)             PerlIO_open(fn, mode)
50           freopen(fn, mode, stream)   PerlIO_reopen(fn, mode, perlio) (Deprecated)
51           fflush(stream)              PerlIO_flush(perlio)
52           fclose(stream)              PerlIO_close(perlio)
53
54   File Input and Output
55           Instead Of:                 Use:
56
57           fprintf(stream, fmt, ...)   PerlIO_printf(perlio, fmt, ...)
58
59           [f]getc(stream)             PerlIO_getc(perlio)
60           [f]putc(stream, n)          PerlIO_putc(perlio, n)
61           ungetc(n, stream)           PerlIO_ungetc(perlio, n)
62
63       Note that the PerlIO equivalents of "fread" and "fwrite" are slightly
64       different from their C library counterparts:
65
66           fread(p, size, n, stream)   PerlIO_read(perlio, buf, numbytes)
67           fwrite(p, size, n, stream)  PerlIO_write(perlio, buf, numbytes)
68
69           fputs(s, stream)            PerlIO_puts(perlio, s)
70
71       There is no equivalent to "fgets"; one should use "sv_gets" instead:
72
73           fgets(s, n, stream)         sv_gets(sv, perlio, append)
74
75   File Positioning
76           Instead Of:                 Use:
77
78           feof(stream)                PerlIO_eof(perlio)
79           fseek(stream, n, whence)    PerlIO_seek(perlio, n, whence)
80           rewind(stream)              PerlIO_rewind(perlio)
81
82           fgetpos(stream, p)          PerlIO_getpos(perlio, sv)
83           fsetpos(stream, p)          PerlIO_setpos(perlio, sv)
84
85           ferror(stream)              PerlIO_error(perlio)
86           clearerr(stream)            PerlIO_clearerr(perlio)
87
88   Memory Management and String Handling
89           Instead Of:                         Use:
90
91           t* p = malloc(n)                    Newx(id, p, n, t)
92           t* p = calloc(n, s)                 Newxz(id, p, n, t)
93           p = realloc(p, n)                   Renew(p, n, t)
94           memcpy(dst, src, n)                 Copy(src, dst, n, t)
95           memmove(dst, src, n)                Move(src, dst, n, t)
96           memcpy(dst, src, sizeof(t))         StructCopy(src, dst, t)
97           memset(dst, 0, n * sizeof(t))       Zero(dst, n, t)
98           memzero(dst, 0)                     Zero(dst, n, char)
99           free(p)                             Safefree(p)
100
101           strdup(p)                   savepv(p)
102           strndup(p, n)               savepvn(p, n) (Hey, strndup doesn't exist!)
103
104           strstr(big, little)         instr(big, little)
105           strcmp(s1, s2)              strLE(s1, s2) / strEQ(s1, s2) / strGT(s1,s2)
106           strncmp(s1, s2, n)          strnNE(s1, s2, n) / strnEQ(s1, s2, n)
107
108       Notice the different order of arguments to "Copy" and "Move" than used
109       in "memcpy" and "memmove".
110
111       Most of the time, though, you'll want to be dealing with SVs internally
112       instead of raw "char *" strings:
113
114           strlen(s)                   sv_len(sv)
115           strcpy(dt, src)             sv_setpv(sv, s)
116           strncpy(dt, src, n)         sv_setpvn(sv, s, n)
117           strcat(dt, src)             sv_catpv(sv, s)
118           strncat(dt, src)            sv_catpvn(sv, s)
119           sprintf(s, fmt, ...)        sv_setpvf(sv, fmt, ...)
120
121       Note also the existence of "sv_catpvf" and "sv_vcatpvfn", combining
122       concatenation with formatting.
123
124       Sometimes instead of zeroing the allocated heap by using Newxz() you
125       should consider "poisoning" the data.  This means writing a bit pattern
126       into it that should be illegal as pointers (and floating point
127       numbers), and also hopefully surprising enough as integers, so that any
128       code attempting to use the data without forethought will break sooner
129       rather than later.  Poisoning can be done using the Poison() macros,
130       which have similar arguments as Zero():
131
132           PoisonWith(dst, n, t, b)    scribble memory with byte b
133           PoisonNew(dst, n, t)        equal to PoisonWith(dst, n, t, 0xAB)
134           PoisonFree(dst, n, t)       equal to PoisonWith(dst, n, t, 0xEF)
135           Poison(dst, n, t)           equal to PoisonFree(dst, n, t)
136
137   Character Class Tests
138       There are two types of character class tests that Perl implements: one
139       type deals in "char"s and are thus not Unicode aware (and hence
140       deprecated unless you know you should use them) and the other type deal
141       in "UV"s and know about Unicode properties. In the following table, "c"
142       is a "char", and "u" is a Unicode codepoint.
143
144           Instead Of:                 Use:            But better use:
145
146           isalnum(c)                  isALNUM(c)      isALNUM_uni(u)
147           isalpha(c)                  isALPHA(c)      isALPHA_uni(u)
148           iscntrl(c)                  isCNTRL(c)      isCNTRL_uni(u)
149           isdigit(c)                  isDIGIT(c)      isDIGIT_uni(u)
150           isgraph(c)                  isGRAPH(c)      isGRAPH_uni(u)
151           islower(c)                  isLOWER(c)      isLOWER_uni(u)
152           isprint(c)                  isPRINT(c)      isPRINT_uni(u)
153           ispunct(c)                  isPUNCT(c)      isPUNCT_uni(u)
154           isspace(c)                  isSPACE(c)      isSPACE_uni(u)
155           isupper(c)                  isUPPER(c)      isUPPER_uni(u)
156           isxdigit(c)                 isXDIGIT(c)     isXDIGIT_uni(u)
157
158           tolower(c)                  toLOWER(c)      toLOWER_uni(u)
159           toupper(c)                  toUPPER(c)      toUPPER_uni(u)
160
161   stdlib.h functions
162           Instead Of:                 Use:
163
164           atof(s)                     Atof(s)
165           atol(s)                     Atol(s)
166           strtod(s, &p)               Nothing.  Just don't use it.
167           strtol(s, &p, n)            Strtol(s, &p, n)
168           strtoul(s, &p, n)           Strtoul(s, &p, n)
169
170       Notice also the "grok_bin", "grok_hex", and "grok_oct" functions in
171       numeric.c for converting strings representing numbers in the respective
172       bases into "NV"s.
173
174       In theory "Strtol" and "Strtoul" may not be defined if the machine perl
175       is built on doesn't actually have strtol and strtoul. But as those 2
176       functions are part of the 1989 ANSI C spec we suspect you'll find them
177       everywhere by now.
178
179           int rand()                  double Drand01()
180           srand(n)                    { seedDrand01((Rand_seed_t)n);
181                                         PL_srand_called = TRUE; }
182
183           exit(n)                     my_exit(n)
184           system(s)                   Don't. Look at pp_system or use my_popen
185
186           getenv(s)                   PerlEnv_getenv(s)
187           setenv(s, val)              my_putenv(s, val)
188
189   Miscellaneous functions
190       You should not even want to use setjmp.h functions, but if you think
191       you do, use the "JMPENV" stack in scope.h instead.
192
193       For "signal"/"sigaction", use "rsignal(signo, handler)".
194

SEE ALSO

196       "perlapi", "perlapio", "perlguts"
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200perl v5.10.1                      2009-02-12                       PERLCLIB(1)
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