getline

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

NAME
       getline, getdelim - delimited string input

SYNOPSIS
       #include <stdio.h>

       ssize_t getline(char **lineptr, size_t *n, FILE *stream);

       ssize_t getdelim(char **lineptr, size_t *n, int delim, FILE *stream);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getline(), getdelim():
           Since glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _GNU_SOURCE

DESCRIPTION
       getline()  reads an entire line from stream, storing the address of the
       buffer containing the text into *lineptr.  The  buffer  is  null-termi-
       nated and includes the newline character, if one was found.

       If  *lineptr  is set to NULL and *n is set 0 before the call, then get-
       line() will allocate a buffer for storing the line.  This buffer should
       be freed by the user program even if getline() failed.

       Alternatively, before calling getline(), *lineptr can contain a pointer
       to a malloc(3)-allocated buffer *n bytes in size.  If the buffer is not
       large  enough  to  hold the line, getline() resizes it with realloc(3),
       updating *lineptr and *n as necessary.

       In either case, on a successful call, *lineptr and *n will  be  updated
       to reflect the buffer address and allocated size respectively.

       getdelim()  works  like  getline(),  except that a line delimiter other
       than newline can be specified as the delimiter argument.  As with  get-
       line(),  a  delimiter  character is not added if one was not present in
       the input before end of file was reached.

RETURN VALUE
       On success, getline() and getdelim() return the  number  of  characters
       read,  including  the delimiter character, but not including the termi-
       nating null byte ('\0').  This value can be  used  to  handle  embedded
       null bytes in the line read.

       Both  functions  return -1 on failure to read a line (including end-of-
       file condition).  In the event of an error, errno is  set  to  indicate
       the cause.

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

       ENOMEM Allocation or reallocation of the line buffer failed.

ATTRIBUTES
       For  an  explanation  of  the  terms  used  in  this  section,  see at-
       tributes(7).

       +----------------------+---------------+---------+
       |Interface             | Attribute     | Value   |
       +----------------------+---------------+---------+
       |getline(), getdelim() | Thread safety | MT-Safe |
       +----------------------+---------------+---------+

CONFORMING TO
       Both getline() and getdelim() were  originally  GNU  extensions.   They
       were standardized in POSIX.1-2008.

EXAMPLE
       #define _GNU_SOURCE
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           FILE *stream;
           char *line = NULL;
           size_t len = 0;
           ssize_t nread;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s <file>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           stream = fopen(argv[1], "r");
           if (stream == NULL) {
               perror("fopen");
               exit(EXIT_FAILURE);
           }

           while ((nread = getline(&line, &len, stream)) != -1) {
               printf("Retrieved line of length %zu:\n", nread);
               fwrite(line, nread, 1, stdout);
           }

           free(line);
           fclose(stream);
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       read(2), fgets(3), fopen(3), fread(3), scanf(3)

COLOPHON
       This  page  is  part of release 5.05 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2019-03-06                        GETLINE(3)