strsep(3)

1strsep(3)                  Library Functions Manual                  strsep(3)
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NAME

6       strsep - extract token from string
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <string.h>
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14       char *strsep(char **restrict stringp, const char *restrict delim);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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18       strsep():
19           Since glibc 2.19:
20               _DEFAULT_SOURCE
21           glibc 2.19 and earlier:
22               _BSD_SOURCE
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DESCRIPTION

25       If  *stringp is NULL, the strsep() function returns NULL and does noth‐
26       ing else.  Otherwise, this function finds the first token in the string
27       *stringp  that  is  delimited  by one of the bytes in the string delim.
28       This token is terminated by overwriting the delimiter with a null  byte
29       ('\0'),  and  *stringp  is updated to point past the token.  In case no
30       delimiter was found, the  token  is  taken  to  be  the  entire  string
31       *stringp, and *stringp is made NULL.
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RETURN VALUE

34       The  strsep()  function returns a pointer to the token, that is, it re‐
35       turns the original value of *stringp.
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ATTRIBUTES

38       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
39       tributes(7).
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41       ┌────────────────────────────────────────────┬───────────────┬─────────┐
42       │Interface                                   │ Attribute     │ Value   │
43       ├────────────────────────────────────────────┼───────────────┼─────────┤
44       │strsep()                                    │ Thread safety │ MT-Safe │
45       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

48       None.
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HISTORY

51       4.4BSD.
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53       The  strsep()  function  was introduced as a replacement for strtok(3),
54       since the latter cannot handle empty fields.  However,  strtok(3)  con‐
55       forms to C89/C99 and hence is more portable.
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BUGS

58       Be cautious when using this function.  If you do use it, note that:
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60       •  This function modifies its first argument.
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62       •  This function cannot be used on constant strings.
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64       •  The identity of the delimiting character is lost.
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EXAMPLES

67       The  program below is a port of the one found in strtok(3), which, how‐
68       ever, doesn't discard multiple delimiters or empty tokens:
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70           $ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'
71           1: a/bbb///cc
72                    --> a
73                    --> bbb
74                    -->
75                    -->
76                    --> cc
77           2: xxx
78                    --> xxx
79           3: yyy
80                    --> yyy
81           4:
82                    -->
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84   Program source
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86       #include <stdio.h>
87       #include <stdlib.h>
88       #include <string.h>
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90       int
91       main(int argc, char *argv[])
92       {
93           char *token, *subtoken;
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95           if (argc != 4) {
96               fprintf(stderr, "Usage: %s string delim subdelim\n", argv[0]);
97               exit(EXIT_FAILURE);
98           }
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100           for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) {
101               printf("%u: %s\n", j, token);
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103               while ((subtoken = strsep(&token, argv[3])))
104                   printf("\t --> %s\n", subtoken);
105           }
106
107           exit(EXIT_SUCCESS);
108       }
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