getline(3)

1GETLINE(3)                 Linux Programmer's Manual                GETLINE(3)
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NAME

6       getline, getdelim - delimited string input
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SYNOPSIS

9       #include <stdio.h>
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11       ssize_t getline(char **lineptr, size_t *n, FILE *stream);
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13       ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       getline(), getdelim():
18           Since glibc 2.10:
19               _POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700
20           Before glibc 2.10:
21               _GNU_SOURCE
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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.
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28       If  *lineptr is NULL, then getline() will allocate a buffer for storing
29       the line, which should be freed by the user program.   (In  this  case,
30       the value in *n is ignored.)
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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.
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37       In either case, on a successful call, *lineptr and *n will  be  updated
38       to reflect the buffer address and allocated size respectively.
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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.
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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.
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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.
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ERRORS

56       EINVAL Bad arguments (n or lineptr is NULL, or stream is not valid).
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VERSIONS

59       These functions are available since libc 4.6.27.
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CONFORMING TO

62       Both  getline()  and  getdelim()  were originally GNU extensions.  They
63       were standardized in POSIX.1-2008.
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EXAMPLE

66       #define _GNU_SOURCE
67       #include <stdio.h>
68       #include <stdlib.h>
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70       int
71       main(void)
72       {
73           FILE *fp;
74           char *line = NULL;
75           size_t len = 0;
76           ssize_t read;
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78           fp = fopen("/etc/motd", "r");
79           if (fp == NULL)
80               exit(EXIT_FAILURE);
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82           while ((read = getline(&line, &len, fp)) != -1) {
83               printf("Retrieved line of length %zu :\n", read);
84               printf("%s", line);
85           }
86
87           free(line);
88           exit(EXIT_SUCCESS);
89       }
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COLOPHON

95       This page is part of release 3.53 of the Linux  man-pages  project.   A
96       description  of  the project, and information about reporting bugs, can
97       be found at http://www.kernel.org/doc/man-pages/.
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101GNU                               2013-04-19                        GETLINE(3)