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