getline, getdelim - delimited string input
#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
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 and
*n is set 0 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 an error,
errno is set to indicate the
cause.
- 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).
Interface |
Attribute |
Value |
getline (), getdelim () |
Thread safety |
MT-Safe |
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 %zu:\n", nread);
fwrite(line, nread, 1, stdout);
}
free(line);
fclose(stream);
exit(EXIT_SUCCESS);
}
read(2),
fgets(3),
fopen(3),
fread(3),
scanf(3)