Manpages - getline.3

getline, getdelim - delimited string input

  #include <stdio.h>

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

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

If *lineptr is set to NULL before the call, then *getline*() 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 *getline*(), a delimiter character is not added if one was not present in the input before end of file was reached.

On success, *getline*() and *getdelim*() return the number of characters read, including the delimiter character, but not including the terminating 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 a failure, errno is set to indicate the error.

EINVAL

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

ENOMEM

Allocation or reallocation of the line buffer failed.

For an explanation of the terms used in this section, see *attributes*(7).

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

  #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 %zd:\n", nread);
          fwrite(line, nread, 1, stdout);
      }

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

*read*(2), *fgets*(3), *fopen*(3), *fread*(3), *scanf*(3)

This page is part of release 5.13 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/.