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man: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
     attributes(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 4.16 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 2017-09-15 GETLINE(3)

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