Assume that the files are .txt
Contents of first file
hello how are you
Contents of second file
I am fine
The desired result is
hello how are you I am fine
Normally what happens is that the original contents are removed and then new contents are added in it.
I want to write in the first file in such a way that its original contents are maintained and the contents of second file are concatenated in it.
Is there any way to do that?
you can append another string in file by opening it in appending mode.
FILE *fp;
fp=fopen("file.txt","a");
here the next string will append after the last pointer of file.For more info link.
Yes, you can open the file with:
fopen("fileName", "a");
This will let you append to the end if the file.
More info is here: http://www.cplusplus.com/reference/cstdio/fopen/
It would help to know how you are trying to write the file. Likely, you are looking for the append option to FOPEN:
http://www.cplusplus.com/reference/cstdio/fopen/
FILE *f = fopen("foo.txt","a");
if (f != NULL) {
/* Use f */
fclose(f);
}
Related
I'm trying to create a file inside a directory, then append some random text inside of the file.
My Code
char dirname[30];
sprintf(dirname, "myroom.%d", (int)getpid());
mkdir(dirname,0777);
char path[path_max+1];
snprintf(path1, PATH_MAX+1, "%s/file1.txt,dirname);
FILE *filedir1 = fopen(path1, "a+");
fclose(filedir1);
char *random_name = { "burger", "toast", "burrito", "noodles" };
int number = rand();
fputs(random_name[number], filedir1];
What I want
(Inside directory "dirname")
When I open file1.txt, I expect there will be either the word burrito, burger, toast, or noodles in the first line.
What I get
file1.txt still empty.
Questions
Anybody know what happen with my code? I saw from youtube video, to append some text into a file, all I need is the fputs command but it doesn't seem to work in my code. Is it because I'm using "a+" in fopen?
Any help will be highly appreciated. Thanks
I think that rand() is creating problem.use rand()%4 instead.
And you are closing the file using fclose() before putting random word. Use it at last.
After opening a file, you are close that file. After closing the file, you are not able to enter the text to that file.
FILE *filedir1 = fopen(path1, "a+");
fclose(filedir1);
Your problem is in this fclose line. You have to do this in after finishing the write operation in that file.
So, remove the fclose(filedir1) and put this line after writing the file.
I am just creating a basic file handling program.
the code is this:
#include <stdio.h>
int main()
{
FILE *p;
p=fopen("D:\\TENLINES.TXT","r");
if(p==0)
{
printf("Error",);
}
fclose(p);
}
This is giving Error, I cannot create files tried reinstalling the compiler and using different locations and names for files but no success.
I am using Windows 7 and compiler is Dev C++ version 5
Change the mode argument in fopen(const char *filename, const char *mode) from:
p=fopen("D:\\TENLINES.TXT","r");//this will not _create_ a file
if(p==0) // ^
To this:
p=fopen("D:\\TENLINES.TXT","w");//this will create a file for writing.
if(p==NULL) // ^ //If the file already exists, it will write over
//existing data.
If you want to add content to an existing file, you can use "a+" for the open mode.
See fopen() (for more open modes, and additional information about the fopen family of functions)
According to tutorial, fopen returns NULL when error occurs. Therefore, you should check if p equals NULL.
Also, in printf("Error",);, omit the comma after string.
Yes you should open the file in write mode.
Which creates the file . Read mode is only to read content
or else you can use "r+" for both read and write.
You should be able to open the file, but you need to make it first. Make a txt document with the name res.txt. It should be able to write your result into the text document.
<?php
$result = $variable1 . $variable2 "=" .$res ."";
echo $result;
$myfile = fopen("res.txt", "a+") or die("nope");
fwrite($myfile, $result);
fclose($myfile)
?>
fopen()
Syntax:
FILE *fp;
fp=fopen(“data.txt”,”r”);
if(fp!=NULL){
//file operations
}
It is necessary to write FILE in the uppercase. The function fopen() will open a file “data.txt”
in read mode.
The fopen() performs the following important task.
It searches the disk for opening the file.
In case the file exists, it loads the file from the disk into memory. If the file is found with huge contents then it loads the file part by part.
If the file does not exist this function returns a NULL. NULL is a macro defined character in the header file “stdio.h”. This indicates that it is unable to open file. There may be following reasons for failure of fopen() functions.
a.When the file is in protected or hidden mode.
b.The file may be used by another program.
It locates a character pointer, which points the first cha
racter of the file. Whenever a file is
opened the character pointer points to the first character of the file
So I'm sort of new to C language, and I'm trying to create a .dat file from other files (like some archiving program). I'm using arguements to specify the files in command line I want to write to my .dat file, and the pack function I wrote seems to be working.
The problem is, I want to create an unpack function too. I'm not sure if this is the easiest way to do this, but I want to copy the argument (the name of the file I want to pack) to it's content, so later, in my unpack function I could search for it inside the .dat file and unpack it.
I'm using this code to write the files to the .dat:
if(!wanttoArchive){
printf("Cannot open %s file\n",argv[i]);
} else {
fseek(wanttoArchive, 0L, SEEK_END);
pos = ftell(wanttoArchive);
fseek(wanttoArchive, 0L, SEEK_SET);
while (pos--){
ch = fgetc(wanttoArchive);
fputc(ch, archived);
}
}
I wanted to use strcat inside the fputc, put it's not working.
Any kind of help would be greatly appreciated!
is there any option to generate an output text file as same as the input file name?
in C i got the file name using:
gets(file_name);
and open it through the:
f1=fopen(file_name,"r");
comment.how do i open the file without entering the format type?
for example for file100.txt i'd like to enter file100 to read the file.
and any option to get the output file as same name as the input file?
You can use
snprintf(new_filename, sizeof new_filename, "%s.%d", File_name, int_val);
For your problem with the file name, you can use e.g. sprintf:
char full_file_name[256];
sprintf(full_file_name, "%s.txt", file_name);
This is not recommended without some validation of the entered file name of course.
For your other problem, from the documentation of fopen:
r+ Open for reading and writing. The stream is positioned at the beginning
of the file.
w+ Open for reading and writing. The file is created if it does not exist,
otherwise it is truncated.
The stream is positioned at the beginning of the file.
a+ Open for reading and appending (writing at end of file). The file is
created if it does not exist.
The initial file position for reading is at the beginning of the file,
but output is always appended to the end of the file.
for creating output file with the same name, simply save your output content into some string. Then, close the file and open it again with write mode("w"). And then, write the content and close the file again.
I'm saving a struct into a .dat file. Lets suppose I have to edit one specific struct, how would I proceed? I did the following:
ptFile = fopen("funcionarios.dat", "ab+");
fseek(ptFile, index*sizeof(strFunc), SEEK_SET); //places the pointer at the struct I want
fwrite(&newStruct, sizeof(strFunc), 1, ptFile); //adds the new struct
So, as you see, I want to update my file with newStruct.
The fwrite functions returns 1, but it does not replace the line I want (nor the neighbor lines, in case I used the missed index), and it doesnt add a new struct to the file. It simply do nothing!
Any ideas?
I did it working by reading all the structs, replacing the index-struct with my newStruct and writing the file with all the structs, but I'm looking for a better way to do that.
Thanks in advance.
fopen(.., "ab+") is asking for append mode:
a+ Open for reading and appending (writing at end of
file). The file is created if it does not exist. The
initial file position for reading is at the beginning
of the file, but output is always appended to the end
of the file.
You probably need r+ mode, which paradoxically also means write:
r+ Open for reading and writing. The stream is
positioned at the beginning of the file.