C语言有getline()函数吗？并帮用程序来详细说明，最好能让初学者都可明白，谢了！

C++有getline()函数.
C 有 fgets(), gets() 函数.

用于读取一行字符直到换行符,包括换行符.
char * fgets ( char * str, int num, FILE * stream );
char * gets ( char * str );

/* gets 例子 */
#include

int main()
{
char string [256];
printf ("Insert your full address: ");
gets (string);
printf ("Your address is: %s\n",string);
return 0;
}

/* fgets 例子 */
#include

int main()
{
FILE * pFile;
char mystring [100];

pFile = fopen ("myfile.txt" , "r");
if (pFile == NULL) perror ("Error opening file");
else {
fgets (mystring , 100 , pFile);
puts (mystring);
fclose (pFile);
}
return 0;
}

c语言没有getline()函数的。我学过c语言的。没有碰到有这函数的。

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

NAME top
getline, getdelim - delimited string input

SYNOPSIS top
#include

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 top
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.

RETURN VALUE top
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.

ERRORS top
EINVAL Bad arguments (n or lineptr is NULL, or stream is not
valid). ENOMEM Allocation or reallocation of the line buffer failed.

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

┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│getline(), getdelim() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘

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

EXAMPLES top
#define _GNU_SOURCE
#include
#include

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 \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 top
read(2), fgets(3), fopen(3), fread(3), scanf(3)

COLOPHON top
This page is part of release 5.12 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 2021-03-22 GETLINE(3)