1GETLINE(3) Linux Programmer's Manual GETLINE(3)
2
6 getline, getdelim - delimited string input
7
9 #include <stdio.h>
10 ssize_t getline(char **restrict lineptr, size_t *restrict n,
12 FILE *restrict stream);
13 ssize_t getdelim(char **restrict lineptr, size_t *restrict n,
14 int delim, FILE *restrict stream);
15 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
17 getline(), getdelim():
19 Since glibc 2.10:
20 _POSIX_C_SOURCE >= 200809L
21 Before glibc 2.10:
22 _GNU_SOURCE
23
25 getline() reads an entire line from stream, storing the address of the
26 buffer containing the text into *lineptr. The buffer is null-termi‐
27 nated and includes the newline character, if one was found.
28 If *lineptr is set to NULL before the call, then getline() will allo‐
30 cate a buffer for storing the line. This buffer should be freed by the
31 user program even if getline() failed.
32 Alternatively, before calling getline(), *lineptr can contain a pointer
34 to a malloc(3)-allocated buffer *n bytes in size. If the buffer is not
35 large enough to hold the line, getline() resizes it with realloc(3),
36 updating *lineptr and *n as necessary.
37 In either case, on a successful call, *lineptr and *n will be updated
39 to reflect the buffer address and allocated size respectively.
40 getdelim() works like getline(), except that a line delimiter other
42 than newline can be specified as the delimiter argument. As with get‐
43 line(), a delimiter character is not added if one was not present in
44 the input before end of file was reached.
45
47 On success, getline() and getdelim() return the number of characters
48 read, including the delimiter character, but not including the termi‐
49 nating null byte ('\0'). This value can be used to handle embedded
50 null bytes in the line read.
51 Both functions return -1 on failure to read a line (including end-of-
53 file condition). In the event of a failure, errno is set to indicate
54 the error.
55
57 EINVAL Bad arguments (n or lineptr is NULL, or stream is not valid).
58 ENOMEM Allocation or reallocation of the line buffer failed.
60
62 For an explanation of the terms used in this section, see at‐
63 tributes(7).
64 ┌────────────────────────────────────────────┬───────────────┬─────────┐
66 │Interface │ Attribute │ Value │
67 ├────────────────────────────────────────────┼───────────────┼─────────┤
68 │getline(), getdelim() │ Thread safety │ MT-Safe │
69 └────────────────────────────────────────────┴───────────────┴─────────┘
70
72 Both getline() and getdelim() were originally GNU extensions. They
73 were standardized in POSIX.1-2008.
74
76 #define _GNU_SOURCE
77 #include <stdio.h>
78 #include <stdlib.h>
79 int
81 main(int argc, char *argv[])
82 {
83 FILE *stream;
84 char *line = NULL;
85 size_t len = 0;
86 ssize_t nread;
87 if (argc != 2) {
89 fprintf(stderr, "Usage: %s <file>\n", argv[0]);
90 exit(EXIT_FAILURE);
91 }
92 stream = fopen(argv[1], "r");
94 if (stream == NULL) {
95 perror("fopen");
96 exit(EXIT_FAILURE);
97 }
98 while ((nread = getline(&line, &len, stream)) != -1) {
100 printf("Retrieved line of length %zd:\n", nread);
101 fwrite(line, nread, 1, stdout);
102 }
103 free(line);
105 fclose(stream);
106 exit(EXIT_SUCCESS);
107 }
108
110 read(2), fgets(3), fopen(3), fread(3), scanf(3)
111
113 This page is part of release 5.12 of the Linux man-pages project. A
114 description of the project, information about reporting bugs, and the
115 latest version of this page, can be found at
116 https://www.kernel.org/doc/man-pages/.
117GNU 2021-03-22 GETLINE(3)