How to read a line from a file in C

c file getline
KaramJaber picture KaramJaber · Nov 6, 2013 · Viewed 47.9k times · Source

I want to read lines from a file line-by-line, but it's not working for me.

Here is what I tried to do:

FILE *file;
char *line = NULL;
int len = 0;
char read;
file=fopen(argv[1], "r");

if (file == NULL)
    return 1;

while ((read = getline(&line, len, file)) != -1) {
    printf("Retrieved line of length %s :\n", &read);
    printf("%s", line);
}

if (line)
    free(line);

return 0;

Any suggestions why that isn't working?

Answer

Leigh picture Leigh · Nov 6, 2013

To get it to work correctly, there's a few changes.

Change int len to size_t len for the correct type.

getline() syntax is incorrect. It should be:

while ((read = getline(&line, &len, file)) != -1) {

And the printf line should also be modified, to print the number returned instead of a char and string interpretation:

printf("Retrieved line of length %d:\n", read);

Related questions

How can I get the list of files in a directory using C or C++?

How can I determine the list of files in a directory from inside my C or C++ code? I'm not allowed to execute the ls command and parse the results from within my program.

Read More
How can I get a file's size in C?

How can I find out the size of a file I opened with an application written in C ? I would like to know the size, because I want to put the content of the loaded file into a string, which …

Read More
Fastest way to check if a file exist using standard C++/C++11/C?

I would like to find the fastest way to check if a file exist in standard C++11, C++, or C. I have thousands of files and before doing something on them I need to check if all of them exist. …

Read More