man3/getline.3

   1 .\" Copyright (c) 2001 John Levon <moz@compsoc.man.ac.uk>
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  24 .TH GETLINE 3  2006-05-17 "GNU" "Linux Programmer's Manual"
  25 .SH NAME
  26 getline, getdelim \- delimited string input
  27 .SH SYNOPSIS
  28 .nf
  29 .B #define _GNU_SOURCE
  30 .B #include <stdio.h>
  31 .sp
  32 .BI "ssize_t getline(char **" lineptr ", size_t *" n ", FILE *" stream );
  33
  34 .BI "ssize_t getdelim(char **" lineptr ", size_t *" n ", int " delim \
  35 ", FILE *" stream );
  36 .fi
  37 .SH DESCRIPTION
  38 .BR getline ()
  39 reads an entire line from \fIstream\fP,
  40 storing the address of the buffer containing the text into
  41 .IR "*lineptr" .
  42 The buffer is null-terminated and includes the newline character, if
  43 one was found.
  44
  45 If
  46 .I "*lineptr"
  47 is NULL, then
  48 .BR getline ()
  49 will allocate a buffer for storing the line,
  50 which should be freed by the user program.
  51 (The value in
  52 .I *n
  53 is ignored.)
  54
  55 Alternatively, before calling
  56 .BR getline (),
  57 .I "*lineptr"
  58 can contain a pointer to a
  59 .BR malloc (3)\-allocated
  60 buffer
  61 .I "*n"
  62 bytes in size.
  63 If the buffer is not large enough to hold the line,
  64 .BR getline ()
  65 resizes it with
  66 .BR realloc (3),
  67 updating
  68 .I "*lineptr"
  69 and
  70 .I "*n"
  71 as necessary.
  72
  73 In either case, on a successful call,
  74 .I "*lineptr"
  75 and
  76 .I "*n"
  77 will be updated to reflect the buffer address and allocated size respectively.
  78
  79 .BR getdelim ()
  80 works like
  81 .BR getline (),
  82 except a line delimiter other than newline can be specified as the
  83 .I delimiter
  84 argument.
  85 As with
  86 .BR getline (),
  87 a delimiter character is not added if one was not present
  88 in the input before end of file was reached.
  89 .SH "RETURN VALUE"
  90 On success,
  91 .BR getline ()
  92 and
  93 .BR getdelim ()
  94 return the number of characters read, including the delimiter character,
  95 but not including the terminating null byte.
  96 This value can be used
  97 to handle embedded null bytes in the line read.
  98
  99 Both functions return \-1  on failure to read a line (including end of file
 100 condition).
 101 .SH ERRORS
 102 .TP
 103 .B EINVAL
 104 Bad parameters
 105 .RI ( n
 106 or
 107 .I lineptr
 108 is NULL, or
 109 .I stream
 110 is not valid).
 111 .SH "CONFORMING TO"
 112 Both
 113 .BR getline ()
 114 and
 115 .BR getdelim ()
 116 are GNU extensions.
 117 They are available since libc 4.6.27.
 118 .SH "EXAMPLE"
 119 .nf
 120 #define _GNU_SOURCE
 121 #include <stdio.h>
 122 #include <stdlib.h>
 123
 124 int
 125 main(void)
 126 {
 127     FILE * fp;
 128     char * line = NULL;
 129     size_t len = 0;
 130     ssize_t read;
 131     fp = fopen("/etc/motd", "r");
 132     if (fp == NULL)
 133         exit(EXIT_FAILURE);
 134     while ((read = getline(&line, &len, fp)) != \-1) {
 135         printf("Retrieved line of length %zu :\en", read);
 136         printf("%s", line);
 137     }
 138     if (line)
 139         free(line);
 140     return EXIT_SUCCESS;
 141 }
 142 .fi
 143 .SH "SEE ALSO"
 144 .BR read (2),
 145 .BR fgets (3),
 146 .BR fopen (3),
 147 .BR fread (3),
 148 .BR gets (3),
 149 .BR scanf (3),
 150 .BR feature_test_macros (7)