getline(3)                                            Library Functions Manual                                           getline(3)

NAME
       getline, getdelim - delimited string input

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #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

DESCRIPTION
       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 neces‐
       sary.

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

       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.

RETURN VALUE
       On  success,  getline()  and getdelim() return the number of characters read, including the delimiter character, but not in‐
       cluding 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.

       If *lineptr was set to NULL before the call, then the buffer should be freed by the user program even on failure.

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 │
       └─────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

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

EXAMPLES
       #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);
       }

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

Linux man-pages 6.03                                         2023-02-05                                                  getline(3)