1 '\" te
   2 .\" Copyright 2014 Garrett D'Amore <garrett@damore.org>
   3 .\" Copyright (c) 2008, Sun Microsystems, Inc.  All Rights Reserved.
   4 .\" Copyright 1989 AT&T
   5 .\" Portions Copyright (c) 1994 Man-cgi 1.15, Panagiotis Christias (christia@softlab.ntua.gr)
   6 .\" Portions Copyright (c) 1996-2008 Modified for NetBSD by Kimmo Suominen (kimmo@suominen.com)
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  15 .TH STRING 3C "Jun 21, 2013"
  16 .SH NAME
  17 string, strcasecmp, strcasecmp_l, strncasecmp, strncasecmp_l, strcat, strncat,
  18 strlcat, strchr, strrchr,
  19 strcmp, strncmp, strcpy, strncpy, strlcpy, strcspn, strspn, strdup, strlen,
  20 strnlen, strpbrk, strsep, strstr, strtok, strtok_r \- string operations
  21 .SH SYNOPSIS
  22 .LP
  23 .nf
  24 #include <strings.h>
  25 
  26 \fBint\fR \fBstrcasecmp\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
  27 .fi
  28 .LP
  29 .nf
  30 \fBint\fR \fBstrcasecmp_l\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR, \fBlocale_t\fR \fIloc\fR);
  31 .fi
  32 .LP
  33 .nf
  34 \fBint\fR \fBstrncasecmp\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR, \fBsize_t\fR \fIn\fR);
  35 .fi
  36 .LP
  37 .nf
  38 \fBint\fR \fBstrncasecmp_l\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR, \fBsize_t\fR \fIn\fR, \fBlocale_t\fR \fIloc\fR);
  39 .fi
  40 .LP
  41 .nf
  42 #include <string.h>
  43 
  44 \fBchar *\fR\fBstrcat\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR);
  45 .fi
  46 .LP
  47 .nf
  48 \fBchar *\fR\fBstrncat\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR, \fBsize_t\fR \fIn\fR);
  49 .fi
  50 .LP
  51 .nf
  52 \fBsize_t\fR \fBstrlcat\fR(\fBchar *\fR\fIdst\fR, \fBconst char *\fR\fIsrc\fR, \fBsize_t\fR \fIdstsize\fR);
  53 .fi
  54 .LP
  55 .nf
  56 \fBchar *\fR\fBstrchr\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
  57 .fi
  58 .LP
  59 .nf
  60 \fBchar *\fR\fBstrrchr\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
  61 .fi
  62 .LP
  63 .nf
  64 \fBint\fR \fBstrcmp\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
  65 .fi
  66 .LP
  67 .nf
  68 \fBint\fR \fBstrncmp\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR, \fBsize_t\fR \fIn\fR);
  69 .fi
  70 .LP
  71 .nf
  72 \fBchar *\fR\fBstrcpy\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR);
  73 .fi
  74 .LP
  75 .nf
  76 \fBchar *\fR\fBstrncpy\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR, \fBsize_t\fR \fIn\fR);
  77 .fi
  78 .LP
  79 .nf
  80 \fBsize_t\fR \fBstrlcpy\fR(\fBchar *\fR\fIdst\fR, \fBconst char *\fR\fIsrc\fR, \fBsize_t\fR \fIdstsize\fR);
  81 .fi
  82 .LP
  83 .nf
  84 \fBsize_t\fR \fBstrcspn\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
  85 .fi
  86 .LP
  87 .nf
  88 \fBsize_t\fR \fBstrspn\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
  89 .fi
  90 .LP
  91 .nf
  92 \fBchar *\fR\fBstrdup\fR(\fBconst char *\fR\fIs1\fR);
  93 .fi
  94 .LP
  95 .nf
  96 \fBsize_t\fR \fBstrlen\fR(\fBconst char *\fR\fIs\fR);
  97 .fi
  98 .LP
  99 .nf
 100 \fBsize_t\fR \fBstrnlen\fR(\fBconst char *\fR\fIs\fR, \fBsize_t\fR \fIn\fR);
 101 .fi
 102 .LP
 103 .nf
 104 \fBchar *\fR\fBstrpbrk\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 105 .fi
 106 .LP
 107 .nf
 108 \fBchar *\fR\fBstrsep\fR(\fBchar **\fR\fIstringp\fR, \fBconst char *\fR\fIdelim\fR);
 109 .fi
 110 .LP
 111 .nf
 112 \fBchar *\fR\fBstrstr\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 113 .fi
 114 .LP
 115 .nf
 116 \fBchar *\fR\fBstrtok\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR);
 117 .fi
 118 .LP
 119 .nf
 120 \fBchar *\fR\fBstrtok_r\fR(\fBchar *restrict\fR \fIs1\fR, \fBconst char *restrict\fR \fIs2\fR,
 121      \fBchar **restrict\fR \fIlasts\fR);
 122 .fi
 123 .SS "ISO C++"
 124 .LP
 125 .nf
 126 #include <string.h>
 127 
 128 \fBconst char *\fR\fBstrchr\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
 129 .fi
 130 .LP
 131 .nf
 132 \fBconst char *\fR\fBstrpbrk\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 133 .fi
 134 .LP
 135 .nf
 136 \fBconst char *\fR\fBstrrchr\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR);
 137 .fi
 138 .LP
 139 .nf
 140 \fBconst char *\fR\fBstrstr\fR(\fBconst char *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 141 .fi
 142 .LP
 143 .nf
 144 #include <cstring>
 145 
 146 \fBchar *std::\fR\fBstrchr\fR(\fBchar *\fR\fIs\fR, \fBint\fR \fIc\fR);
 147 .fi
 148 .LP
 149 .nf
 150 \fBchar *std::\fR\fBstrpbrk\fR(\fBchar *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 151 .fi
 152 .LP
 153 .nf
 154 \fBchar *std::\fR\fBstrrchr\fR(\fBchar *\fR\fIs\fR, \fBint\fR \fIc\fR);
 155 .fi
 156 .LP
 157 .nf
 158 \fBchar *std::\fR\fBstrstr\fR(\fBchar *\fR\fIs1\fR, \fBconst char *\fR\fIs2\fR);
 159 .fi
 160 .SH DESCRIPTION
 161 .LP
 162 The arguments \fIs\fR, \fIs1\fR, and \fIs2\fR point to strings (arrays of
 163 characters terminated by a null character). The \fBstrcat()\fR,
 164 \fBstrncat()\fR, \fBstrlcat()\fR, \fBstrcpy()\fR, \fBstrncpy()\fR,
 165 \fBstrlcpy()\fR, \fBstrsep()\fR, \fBstrtok()\fR, and \fBstrtok_r()\fR functions
 166 all alter their first argument. Additionally, the \fBstrcat()\fR and
 167 \fBstrcpy()\fR functions do not check for overflow of the array.
 168 .SS "\fBstrcasecmp()\fR, \fBstrncasecmp()\fR"
 169 .sp
 170 .LP
 171 The \fBstrcasecmp()\fR and \fBstrncasecmp()\fR functions are case-insensitive
 172 versions of  \fBstrcmp()\fR and \fBstrncmp()\fR respectively, described below.
 173 .LP
 174 The \fBstrcasecmp()\fR and \fBstrncasecmp()\fR functions compare two strings
 175 byte-by-byte, after
 176 converting each upper-case character to lower-case (as determined by the
 177 \fBLC_CTYPE\fR category of the current locale).  Note that neither the contents
 178 pointed to by \fIs1\fR nor \fIs2\fR are modified.
 179 .LP
 180 The functions return an integer
 181 greater than, equal to, or less than 0, if the string pointed to by \fIs1\fR
 182 is greater than, equal to, or less than the string pointed to by \fIs2\fR
 183 respectively. The sign of a non-zero return value is determined  by the sign of
 184 the difference between the values of the first pair of bytes that differ in the
 185 .LP
 186 The \fBstrncasecmp()\fR function examines at most \fIn\fR bytes from each
 187 string.
 188 .SS "\fBstrcasecmp_l()\fR, \fBstrncasecmp_l()\fR"
 189 .LP
 190 The \fBstrcasecmp_l()\fR and \fBstrncasecmp_l()\fR functions behave identically
 191 to \fBstrcasecmp()\fR and \fBstrncasecmp()\fR, except instead of operating in
 192 the current locale, they instead operate in the locale specified by \fIloc\fR.
 193 .SS "\fBstrcat()\fR, \fBstrncat()\fR, \fBstrlcat()\fR"
 194 .LP
 195 The \fBstrcat()\fR function appends a copy of string \fIs2\fR, including the
 196 terminating null character, to the end of string \fIs1\fR. The \fBstrncat()\fR
 197 function appends at most \fIn\fR characters. Each returns a pointer to the
 198 null-terminated result. The initial character of  \fIs2\fR overrides the null
 199 character at the end of \fIs1\fR. If copying takes place between objects that
 200 overlap, the behavior of \fBstrcat()\fR, \fBstrncat()\fR, and \fBstrlcat()\fR
 201 is undefined.
 202 .LP
 203 The \fBstrlcat()\fR function appends  at most
 204 (\fIdstsize\fR-\fBstrlen\fR(\fIdst\fR)-1) characters of \fIsrc\fR to \fIdst\fR
 205 (\fIdstsize\fR being the  size of the  string buffer \fIdst\fR). If the string
 206 pointed to by \fIdst\fR contains a null-terminated string that fits into
 207 \fIdstsize\fR bytes when \fBstrlcat()\fR is called, the string pointed to by
 208 \fIdst\fR will be a null-terminated string that fits in \fIdstsize\fR bytes
 209 (including the terminating null character) when it completes, and the initial
 210 character of \fIsrc\fR will override the null character at  the end of
 211 \fIdst\fR. If the string pointed to by \fIdst\fR is longer than \fIdstsize\fR
 212 bytes when \fBstrlcat()\fR is called, the string pointed to by \fIdst\fR will
 213 not be changed. The function returns
 214 \fBmin\fR{\fIdstsize\fR,\fBstrlen\fR(\fIdst\fR)}+\fBstrlen\fR(\fIsrc\fR).
 215 Buffer overflow can be checked as  follows:
 216 .sp
 217 .in +2
 218 .nf
 219 if (strlcat(dst, src, dstsize) >= dstsize)
 220         return \(mi1;
 221 .fi
 222 .in -2
 223 .SS "\fBstrchr()\fR, \fBstrrchr()\fR"
 224 .LP
 225 The \fBstrchr()\fR function returns a pointer to the first occurrence of
 226 \fIc\fR (converted to a  \fBchar\fR) in string \fIs\fR, or a null pointer if
 227 \fIc\fR does not occur in the string. The \fBstrrchr()\fR function returns a
 228 pointer to the last occurrence of \fIc\fR. The null character terminating a
 229 string is considered to be part of the string.
 230 .SS "\fBstrcmp()\fR, \fBstrncmp()\fR"
 231 .LP
 232 The \fBstrcmp()\fR function compares two strings byte-by-byte, according to the
 233 ordering of your machine's character set.  The function returns an integer
 234 greater than, equal to, or less than 0, if  the string pointed to by \fIs1\fR
 235 is greater than, equal to, or less than the string pointed to by \fIs2\fR
 236 respectively. The sign of a non-zero return value is determined  by the sign of
 237 the difference between the values of the first pair of bytes that differ in the
 238 strings being compared. The \fBstrncmp()\fR function makes the same comparison
 239 but looks at a maximum of \fIn\fR bytes. Bytes following a null byte are not
 240 compared.
 241 .SS "\fBstrcpy()\fR, \fBstrncpy()\fR, \fBstrlcpy()\fR"
 242 .LP
 243 The \fBstrcpy()\fR function copies string \fIs2\fR to \fIs1\fR, including the
 244 terminating null character, stopping after the null character has been copied.
 245 The \fBstrncpy()\fR function copies exactly \fIn\fR bytes, truncating \fIs2\fR
 246 or adding null characters to \fIs1\fR if necessary. The result will not be
 247 null-terminated if the length of \fIs2\fR is \fIn\fR or more. Each function
 248 returns \fIs1\fR.  If copying takes place between objects that overlap, the
 249 behavior of \fBstrcpy()\fR, \fBstrncpy()\fR, and \fBstrlcpy()\fR is undefined.
 250 .LP
 251 The \fBstrlcpy()\fR function copies  at most \fIdstsize\fR\(mi1 characters
 252 (\fIdstsize\fR being the  size of the  string buffer \fIdst\fR) from \fIsrc\fR
 253 to \fIdst\fR,  truncating \fIsrc\fR if necessary.  The  result is always
 254 null-terminated. The function returns \fBstrlen\fR(\fIsrc\fR). Buffer overflow
 255 can be checked as  follows:
 256 .sp
 257 .in +2
 258 .nf
 259 if (strlcpy(dst, src, dstsize) >= dstsize)
 260         return \(mi1;
 261 .fi
 262 .in -2
 263 
 264 .SS "\fBstrcspn()\fR, \fBstrspn()\fR"
 265 .LP
 266 The \fBstrcspn()\fR function returns the length of the initial segment of
 267 string \fIs1\fR that consists entirely of characters not from string \fIs2\fR.
 268 The \fBstrspn()\fR function returns the length of the initial segment of string
 269 \fIs1\fR that consists entirely of characters from string \fIs2\fR.
 270 .SS "\fBstrdup()\fR"
 271 .LP
 272 The \fBstrdup()\fR function returns a pointer to a new string that is a
 273 duplicate of the string pointed to by  \fIs1\fR. The returned pointer can be
 274 passed to \fBfree()\fR. The space for the new string is obtained using
 275 \fBmalloc\fR(3C). If the new string cannot be created, a null pointer is
 276 returned and \fBerrno\fR may be set to \fBENOMEM\fR to indicate that the
 277 storage space available is insufficient.
 278 .SS "\fBstrlen()\fR, \fBstrnlen()\fR"
 279 .sp
 280 The \fBstrlen()\fR function returns the number of bytes in \fIs\fR, not
 281 including the terminating null character.
 282 .LP
 283 The \fBstrnlen()\fR function returns the smaller of \fIn\fR or the number of
 284 bytes in \fIs\fR, not including the terminating null character. The
 285 \fBstrnlen()\fR function never examines more than \fIn\fR bytes of the string
 286 pointed to by \fIs\fR.
 287 .SS "\fBstrpbrk()\fR"
 288 .LP
 289 The \fBstrpbrk()\fR function returns a pointer to the first occurrence in
 290 string \fIs1\fR of any character from string \fIs2\fR, or a null pointer if no
 291 character from \fIs2\fR exists in \fIs1\fR.
 292 .SS "\fBstrsep()\fR"
 293 .LP
 294 The \fBstrsep()\fR function locates, in the null-terminated string referenced
 295 by *\fIstringp\fR, the first occurrence of any character in the string
 296 \fIdelim\fR (or the terminating `\e0' character) and replaces it with a `\e0'.
 297 The location of the next character after the delimiter character (or
 298 \fINULL\fR, if the end of the string was reached) is stored in *\fIstringp\fR.
 299 The original value of *\fIstringp\fR is returned.
 300 .LP
 301 An ``empty'' field (one caused by two adjacent delimiter characters) can be
 302 detected by comparing the location referenced by the pointer returned by
 303 \fBstrsep()\fR to `\e0'.
 304 .LP
 305 If *\fIstringp\fR is initially \fINULL\fR, \fBstrsep()\fR returns \fINULL\fR.
 306 .SS "\fBstrstr()\fR"
 307 .LP
 308 The \fBstrstr()\fR function locates the first occurrence of the string \fIs2\fR
 309 (excluding the terminating null character) in string \fIs1\fR and returns a
 310 pointer to the located string, or a null pointer if the string is not found. If
 311 \fIs2\fR points to a string with zero length (that is, the string \fB""\fR),
 312 the function returns  \fIs1\fR.
 313 .SS "\fBstrtok()\fR"
 314 .LP
 315 A sequence of calls to \fBstrtok()\fR breaks the string pointed to by \fIs1\fR
 316 into a sequence of tokens, each of which is delimited by a byte from the string
 317 pointed to by \fIs2\fR. The first call in the sequence has \fIs1\fR as its
 318 first argument, and is followed by calls with a null pointer as their first
 319 argument. The separator string pointed to by \fIs2\fR can be different from
 320 call to call.
 321 .LP
 322 The first call in the sequence searches the string pointed to by \fIs1\fR for
 323 the first byte that is not contained in the current separator string pointed to
 324 by \fIs2\fR. If no such byte is found, then there are no tokens in the string
 325 pointed to by \fIs1\fR and \fBstrtok()\fR returns a null pointer. If such a
 326 byte is found, it is the start of the first token.
 327 .LP
 328 The \fBstrtok()\fR function then searches from there for a byte that is
 329 contained in the current separator string. If no such byte is found, the
 330 current token extends to the end of the string pointed to by \fIs1\fR, and
 331 subsequent searches for a token return a null pointer. If such a byte is found,
 332 it is overwritten by a null byte that terminates the current token. The
 333 \fBstrtok()\fR function saves a pointer to the following byte in
 334 thread-specific data, from which the next search for a token starts.
 335 .LP
 336 Each subsequent call, with a null pointer as the value of the first argument,
 337 starts searching from the saved pointer and behaves as described above.
 338 .LP
 339 See Example 1, 2, and 3 in the \fBEXAMPLES\fR section for examples of
 340 \fBstrtok()\fR usage and the explanation in \fBNOTES\fR.
 341 .SS "\fBstrtok_r()\fR"
 342 .LP
 343 The \fBstrtok_r()\fR function considers the null-terminated string \fIs1\fR as
 344 a sequence of zero or more text tokens separated by spans of one or more
 345 characters from the separator string \fIs2\fR. The argument \fIlasts\fR points
 346 to a user-provided pointer which points to stored information necessary for
 347 \fBstrtok_r()\fR to continue scanning the same string.
 348 .LP
 349 In the first call to \fBstrtok_r()\fR, \fIs1\fR points to a null-terminated
 350 string, \fIs2\fR to a null-terminated string of separator characters, and the
 351 value pointed to by \fIlasts\fR is ignored. The \fBstrtok_r()\fR function
 352 returns a pointer to the first character of the first token, writes a null
 353 character into \fIs1\fR immediately following the returned token, and updates
 354 the pointer to which \fIlasts\fR points.
 355 .LP
 356 In subsequent calls, \fIs1\fR is a null pointer and \fIlasts\fR is unchanged
 357 from the previous call so that subsequent calls move through the string
 358 \fIs1\fR, returning successive tokens until no tokens remain. The separator
 359 string \fIs2\fR can be different from call to call. When no token remains in
 360 \fIs1\fR, a null pointer is returned.
 361 .LP
 362 See Example 3 in the \fBEXAMPLES\fR section for an example of \fBstrtok_r()\fR
 363 usage and the explanation in \fBNOTES\fR.
 364 .SH EXAMPLES
 365 .LP
 366 \fBExample 1 \fRSearch for word separators.
 367 .LP
 368 The following example searches for tokens separated by space characters.
 369 
 370 .sp
 371 .in +2
 372 .nf
 373 #include <string.h>
 374 \&...
 375 char *token;
 376 char line[] = "LINE TO BE SEPARATED";
 377 char *search = " ";
 378 
 379 /* Token will point to "LINE". */
 380 token = strtok(line, search);
 381 
 382 /* Token will point to "TO". */
 383 token = strtok(NULL, search);
 384 .fi
 385 .in -2
 386 
 387 .LP
 388 \fBExample 2 \fRBreak a Line.
 389 .LP
 390 The following example uses strtok to break a line into two character strings
 391 separated by any combination of SPACEs, TABs, or NEWLINEs.
 392 
 393 .sp
 394 .in +2
 395 .nf
 396 #include <string.h>
 397 \&...
 398 struct element {
 399        char *key;
 400        char *data;
 401 };
 402 \&...
 403 char line[LINE_MAX];
 404 char *key, *data;
 405 \&...
 406 key = strtok(line, " \en");
 407 data = strtok(NULL, " \en");
 408 .fi
 409 .in -2
 410 
 411 .LP
 412 \fBExample 3 \fRSearch for tokens.
 413 .LP
 414 The following example uses both \fBstrtok()\fR and \fBstrtok_r()\fR to search
 415 for tokens separated by one or more characters from the string pointed to by
 416 the second argument, "/".
 417 
 418 .sp
 419 .in +2
 420 .nf
 421 #define __EXTENSIONS__
 422 #include <stdio.h>
 423 #include <string.h>
 424 
 425 int
 426 main() {
 427         char *buf="5/90/45";
 428         char *token;
 429         char *lasts;
 430 
 431         printf("tokenizing \e"%s\e" with strtok():\en", buf);
 432         if ((token = strtok(buf, "/")) != NULL) {
 433                 printf("token = "%s\e"\en", token);
 434                 while ((token = strtok(NULL, "/")) != NULL) {
 435                         printf("token = \e"%s\e"\en", token);
 436                 }
 437         }
 438 
 439         buf = "//5//90//45//";
 440         printf("\entokenizing \e"%s\e" with strtok_r():\en", buf);
 441         if ((token = strtok_r(buf, "/", &lasts)) != NULL) {
 442                 printf("token = \e"%s\e"\en", token);
 443                 while ((token = strtok_r(NULL, "/", &lasts)) != NULL) {
 444                         printf("token = \e"%s\e"\en", token);
 445                 }
 446         }
 447 }
 448 .fi
 449 .in -2
 450 
 451 .LP
 452 When compiled and run, this example produces the following output:
 453 
 454 .sp
 455 .in +2
 456 .nf
 457 tokenizing "5/90/45" with \fBstrtok()\fR:
 458 token = "5"
 459 token = "90"
 460 token = "45"
 461 
 462 tokenizing "//5//90//45//" with \fBstrtok_r()\fR:
 463 token = "5"
 464 token = "90"
 465 token = "45"
 466 .fi
 467 .in -2
 468 
 469 .SH ATTRIBUTES
 470 .LP
 471 See \fBattributes\fR(5) for descriptions of the following attributes:
 472 .TS
 473 box;
 474 c | c
 475 l | l .
 476 ATTRIBUTE TYPE  ATTRIBUTE VALUE
 477 _
 478 Interface Stability     See below.
 479 _
 480 MT-Level        See below.
 481 _
 482 Standard        See below.
 483 .TE
 484 
 485 .LP
 486 The
 487 \fBstrlcat()\fR, \fBstrlcpy()\fR, and \fBstrsep()\fR functions are Committed.
 488 All the rest are Standard.
 489 .LP
 490 The \fBstrtok()\fR and \fBstrdup()\fR functions are MT-Safe. The remaining
 491 functions are Async-Signal-Safe.
 492 .LP
 493 For all except \fBstrlcat()\fR, \fBstrlcpy()\fR, and \fBstrsep()\fR, see
 494 \fBstandards\fR(5).
 495 .SH SEE ALSO
 496 .LP
 497 \fBmalloc\fR(3C),
 498 \fBnewlocale(3C), \fBsetlocale\fR(3C), \fBstrxfrm\fR(3C), \fBuselocale\fR(3C),
 499 \fBattributes\fR(5), \fBstandards\fR(5)
 500 .SH NOTES
 501 .LP
 502 When compiling multithreaded applications, the \fB_REENTRANT\fR flag must be
 503 defined on the compile line. This flag should only be used in multithreaded
 504 applications.
 505 .LP
 506 A single-threaded application can gain access to \fBstrtok_r()\fR only by
 507 defining \fB__EXTENSIONS__\fR or by defining \fB_POSIX_C_SOURCE\fR to a value
 508 greater than or equal to 199506L.
 509 .LP
 510 Except where noted otherwise, all of these functions assume the default
 511 locale ``C.'' For some locales,
 512 \fBstrxfrm\fR(3C) should be applied to the strings before they are passed to
 513 the functions.
 514 .LP
 515 The \fBstrtok()\fR function is safe to use in multithreaded applications
 516 because it saves its internal state in a thread-specific data area.  However,
 517 its use is discouraged, even for single-threaded applications. The
 518 \fBstrtok_r()\fR function should be used instead.
 519 .LP
 520 Do not pass the address of a character string literal as the argument \fIs1\fR
 521 to either \fBstrtok()\fR or \fBstrtok_r()\fR. Similarly, do not pass a pointer
 522 to the address of a character string literal as the argument \fIstringp\fR to
 523 \fBstrsep()\fR. These functions can modify the storage pointed to by \fIs1\fR
 524 in the case of \fBstrtok()\fR and \fBstrtok_r()\fR or *\fIstringp\fR in the
 525 case of \fBstrsep()\fR. The C99 standard specifies that attempting to modify
 526 the storage occupied by a string literal results in undefined behavior. This
 527 allows compilers (including \fBgcc\fR and the Sun Studio compilers when the
 528 \fB-xstrconst\fR flag is used) to place string literals in read-only memory.
 529 Note that in Example 1 above, this problem is avoided because the variable
 530 \fIline\fR is declared as a writable array of type \fBchar\fR that is
 531 initialized by a string literal rather than a pointer to \fBchar\fR that points
 532 to a string literal.