getline(3)

1GETLINE(3)                 Linux Programmer's Manual                GETLINE(3)
2
3
4

NAME

6       getline, getdelim - delimited string input
7

SYNOPSIS

9       #include <stdio.h>
10
11       ssize_t getline(char **lineptr, size_t *n, FILE *stream);
12
13       ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream);
14
15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
16
17       getline(), getdelim():
18           Since glibc 2.10:
19               _POSIX_C_SOURCE >= 200809L
20           Before glibc 2.10:
21               _GNU_SOURCE
22

DESCRIPTION

24       getline()  reads an entire line from stream, storing the address of the
25       buffer containing the text into *lineptr.  The  buffer  is  null-termi‐
26       nated and includes the newline character, if one was found.
27
28       If  *lineptr  is set to NULL and *n is set 0 before the call, then get‐
29       line() will allocate a buffer for storing the line.  This buffer should
30       be freed by the user program even if getline() failed.
31
32       Alternatively, before calling getline(), *lineptr can contain a pointer
33       to a malloc(3)-allocated buffer *n bytes in size.  If the buffer is not
34       large  enough  to  hold the line, getline() resizes it with realloc(3),
35       updating *lineptr and *n as necessary.
36
37       In either case, on a successful call, *lineptr and *n will  be  updated
38       to reflect the buffer address and allocated size respectively.
39
40       getdelim()  works  like  getline(),  except that a line delimiter other
41       than newline can be specified as the delimiter argument.  As with  get‐
42       line(),  a  delimiter  character is not added if one was not present in
43       the input before end of file was reached.
44

RETURN VALUE

46       On success, getline() and getdelim() return the  number  of  characters
47       read,  including  the delimiter character, but not including the termi‐
48       nating null byte ('\0').  This value can be  used  to  handle  embedded
49       null bytes in the line read.
50
51       Both  functions  return -1 on failure to read a line (including end-of-
52       file condition).  In the event of an error, errno is  set  to  indicate
53       the cause.
54

ERRORS

56       EINVAL Bad arguments (n or lineptr is NULL, or stream is not valid).
57
58       ENOMEM Allocation or reallocation of the line buffer failed.
59

ATTRIBUTES

61       For   an   explanation   of   the  terms  used  in  this  section,  see
62       attributes(7).
63
64       ┌──────────────────────┬───────────────┬─────────┐
65       │Interface             │ Attribute     │ Value   │
66       ├──────────────────────┼───────────────┼─────────┤
67       │getline(), getdelim() │ Thread safety │ MT-Safe │
68       └──────────────────────┴───────────────┴─────────┘
69

CONFORMING TO

71       Both getline() and getdelim() were  originally  GNU  extensions.   They
72       were standardized in POSIX.1-2008.
73

EXAMPLE

75       #define _GNU_SOURCE
76       #include <stdio.h>
77       #include <stdlib.h>
78
79       int
80       main(int argc, char *argv[])
81       {
82           FILE *stream;
83           char *line = NULL;
84           size_t len = 0;
85           ssize_t nread;
86
87           if (argc != 2) {
88               fprintf(stderr, "Usage: %s <file>\n", argv[0]);
89               exit(EXIT_FAILURE);
90           }
91
92           stream = fopen(argv[1], "r");
93           if (stream == NULL) {
94               perror("fopen");
95               exit(EXIT_FAILURE);
96           }
97
98           while ((nread = getline(&line, &len, stream)) != -1) {
99               printf("Retrieved line of length %zu:\n", nread);
100               fwrite(line, nread, 1, stdout);
101           }
102
103           free(line);
104           fclose(stream);
105           exit(EXIT_SUCCESS);
106       }
107

COLOPHON

112       This  page  is  part of release 5.02 of the Linux man-pages project.  A
113       description of the project, information about reporting bugs,  and  the
114       latest     version     of     this    page,    can    be    found    at
115       https://www.kernel.org/doc/man-pages/.
116
117
118
119GNU                               2019-03-06                        GETLINE(3)