Article directory
- C language file operation
-
- read file
- write file
- Other operations
-
- File pointer relocation
- Get pointer position
- Get file size
- Rename file
- Delete Files
- C++ file operations
-
- read file
- read file
- Windows file operations
-
- read file
- write file
- Other operations
-
- Copy files
- Delete files/directories
- Determine whether the directory exists
- Traverse files and directories under a directory
- ATL read and write files
- Linux file operations
C language file operation
| File access mode string | Meaning | If the file does not exist, the actual action |
|---|---|---|
| “r” | Read from the beginning | Open failed |
| “w | Overwrite | Create new file |
| “a” | Append write | Create new File |
| “r +” | Overlay readable and writable | Error |
| “w + ” | Overwriting readable and writable | Create new file |
| “a + ” | Append readable and writable | Create new file |
| “rb” | Read binary from the beginning | Open failed |
| “wb” | Overwrite binary | Create new file |
| “ab” | Append write binary | Create new file |
| “rb +” | Overlay readable and writable binary | Error |
| “wb +” | Overlay can Read and write binary | Create new file |
| “ab +” | Append read and write binary | Create new file |
Read file
#include <stdio.h>
int main() {<!-- -->
// 1. Open the file
FILE* fr = fopen("E:\\work\testFile\messfile\23-11-6\1.txt", "r") ; //Open the file for reading
if (fr == NULL) {<!-- --> //file is NULL, then the file fails to open and the program exits.
printf("File cannot be opened! \\
");
return -1;
}
// 2. Read content
char buf[0xFF] = {<!-- --> 0 };
// 2.1 Read in byte blocks
while (!feof(fr)) //Not to the end of the file
{<!-- -->
memset(buf, 0, sizeof(buf));
size_t len = fread(buf, sizeof(char), sizeof(buf), fr); //Read sizeof(char) bytes each time, read sizeof(buf) times, you can also use the fscanf function
printf("buf: %s, len: %d\\
", buf, len);
}
// 2.2 Read by word line. There will be bugs in reading Chinese with this method.
char* str = NULL;
while (!feof(fr))
{<!-- -->
memset(buf, 0, sizeof(buf));
str = fgets(buf, sizeof(buf), fr); //fgets can read up to sizeof(buf) bytes at a time and will stop reading when it encounters a newline character.
printf("buf: %s \\
", buf);
printf("str: %s \\
", str); //Str content is the same as buf content
}
// 2.3 Read by character
char c = 0;
while (c != EOF)
{<!-- -->
c = fgetc(fr); // Get a character
printf("%c", c);
}
printf("\\
");
// 3. Close the file
if (fclose(fr) != 0)
{<!-- -->
printf("File cannot be closed! \\
");
return -1;
}
else
{<!-- -->
printf("File is now closed! \\
");
}
return 0;
}
Write file
#include <stdio.h>
int main(int argc, char* argv[])
{<!-- -->
// 1. Open the file
FILE* fw = fopen("E:\work\testFile\messfile\23-11-6\1.txt", "w") ; //Open the file for reading
if (fw == NULL) {<!-- --> //file is NULL, then the file fails to open and the program exits.
printf("File cannot be opened! \\
");
return -1;
}
// 2. Write content
char buf[128] = {<!-- --> 0 };
\t
// 2.1 Write by data block
char str[] = "Nanpu is sad and sad, and the west phoenix curls up in autumn.";
memcpy(buf, str, strlen(str));
fwrite(buf, strlen(buf) + 1, 1, fw); //Write strlen(buf) bytes each time, once. You can use the fprint function
// 2.2 Write row by row
while (NULL != fgets(buf, sizeof(buf), stdin)) {<!-- -->
printf("Read line with len: %d\\
", strlen(buf));
fputs(buf, fw);
fflush(fw); //Refresh the output buffer
printf("%s", buf);
}
\t
// 2.3 Write by character
char ch = getchar();
while (ch != '$')
{<!-- -->
fputc(ch, fw);
ch = getchar();
}
// 3. Close the file
if (fclose(fw) != 0)
{<!-- -->
printf("File cannot be closed! \\
");
return -1;
}
else
{<!-- -->
printf("File is now closed! \\
");
}
\t
return 0;
}
Other operations
File pointer relocation
int fseek (FILE * stream, long int offset, int origin);
stream: stream
offset: the offset corresponding to the origin position, in bytes
origin: the position of the pointer
#define SEEK_CUR 1 // current position
#define SEEK_END 2 // end
#define SEEK_SET 0 // start
Get pointer position
long int ftell (FILE * stream);
Get file size
long n; fseek(pf,0,SEEK_END); n=ftell(pf);
Rename file
int rename ( const char * oldname, const char * newname );
oldname: original name
newname: new name
Delete files
int remove ( const char * filename );
filename: full path to the file
C++ file operations
| Open method | Meaning |
|---|---|
| ios::in | Read from beginning |
| ios::out | Overwrite write |
| ios:: ate | Put the file pointer to the end |
| ios::app | Append writing |
| ios::trunc | Clear content |
| ios::binary | Open in binary mode |
Read file
#include <fstream>
#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{<!-- -->
// 1. Open the file
fstream fr;
fr.open("1.txt", ios::in); //Open the file in read-only mode
if (!fr.is_open())
std::cerr << "cannot open the file!" << endl;
\t
// 2. Read content
char buf[1024] = {<!-- --> 0 };
// 2.1 Read by element
while (fr >> buf)
cout << buf << endl; //Each buf is an element separated by spaces or enter keys
// 2.2 Fetch by row
while (fr.getline(buf, sizeof(buf)))
std::cout << buf << std::endl;
// 2.3 Read by character
char c;
while ((c = fr.get()) != EOF)
std::cout << c;
// 2.4 is often used to read and write binary files, but can also read non-binary files.
fr.read((char*)buf, sizeof(buf)); //Read into buf, read sizeof(buf) bytes
cout << buf;
// 3. Close the file
fr.close();
\t
return 0;
}
Read file
#include <fstream>
#include <iostream>
using namespace std;
int main(int argc, char* argv[])
{<!-- -->
// 1. Open the file
ofstream fw;
fw.open("1.txt", ios::app); //Open the file in append writing mode
if (!fw.is_open())
std::cerr << "cannot open the file!" << endl;
\t
// 2. Write content
// 2.1 Direct writing
fw << "If the heart is broken, Xinfeng wine will be lost, and thousands of sorrows will be spent." << endl;
// 2.2 Commonly used for binary writing, can also be used for ordinary file writing
char buf[1024] = "I am not famous yet and I am not married, so I may not be as good as others.";
fw.write((char*)buf, strlen(buf));
\t
// 3. Close the file
fw.close();
\t
system("pause");
return 0;
}
Windows file operations
Read file
#include <windows.h>
int main(int argc, char* argv[])
{<!-- -->
// 1. Open the file
HANDLE hFile = CreateFile("1.txt", GENERIC_READ, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == NULL) {<!-- -->
return -1;
}
// 2. Read the file
char buf[128] = {<!-- --> 0 };
DWORD len = 0;
DWORD dwBytesToRead = GetFileSize(hFile, NULL); //Get the file size
\t
do {<!-- --> //Loop through the file to ensure that the complete file is read out
if (!ReadFile(hFile, buf, dwBytesToRead, & amp;len, NULL)) {<!-- -->
cout << "read file error!" << GetLastError() << endl;
return -1;
}
cout << buf << endl;
dwBytesToRead -= len;
} while (dwBytesToRead > 0);
// 3. Close the file
CloseHandle(hFile);
return 0;
}
Write file
int main(int argc, char* argv[])
{<!-- -->
// 1. Open the file
HANDLE hFile = CreateFile("1.txt", GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == NULL) {<!-- -->
return -1;
}
SetFilePointer(hFile, 0, NULL, FILE_END); //Set the file pointer to the end of the file to implement additional writing
// 2. Write file
char buf[128] = {<!-- --> 0 };
DWORD len = 0;
char str[] = "Lao Ge Yiyi explains boating, red leaves, green mountains and rapids, the sunset is sober and people are far away, the sky is full of wind and rain, and I am descending to the west building.";
memcpy(buf, str, strlen(str));
WriteFile(hFile, buf, strlen(buf), &len, NULL);
FlushFileBuffers(hFile); //Refresh cache
\t
// 3. Close the file
CloseHandle(hFile);
system("pause");
return 0;
}
Other operations
Copy files
CopyFile()
Delete files/directories
deleteFiles(dir)
Determine whether the directory exists
#include<io.h> if (!GetFileAttributesA(mTempDir.c_str()) & amp; FILE_ATTRIBUTE_DIRECTORY) //Whether the mTempDir directory exists, create the directory if it does not exist resultFlag = CreateDirectory(mTempDir.c_str(), NULL);
Traverse files and directories under a directory
//File handle, win10 uses long long, win7 uses long.
long long hFile = 0;
//File information
struct _finddata_t fileinfo;
if ((hFile = _findfirst(p.assign(path).append("\*").c_str(), & amp;fileinfo)) != -1) //The first search combination Check whether the directory or file exists
{<!-- -->
do
{<!-- -->
if ((fileinfo.attrib & amp; _A_SUBDIR))//If it is a directory, iterate over it
{<!-- -->
if (strcmp(fileinfo.name, ".") != 0 & amp; & amp; strcmp(fileinfo.name, "..") != 0)
getFiles(p.assign(path).append("\").append(fileinfo.name), files, names);
}
else//If not, add to the list
files.push_back(p.assign(path).append("\").append(fileinfo.name));
} while (_findnext(hFile, & amp;fileinfo) == 0);
_findclose(hFile);
}
ATL read and write files
#include<atlfile.h>
using namespace std;
int main(int argc, char* argv[])
{<!-- -->
CAtlFile file;
file.Create(L"1.txt", GENERIC_WRITE, 0, OPEN_EXISTING);
char buf[128] = "The Big Dipper is horizontal in the sky and the night is dark, and people are worried about leaning on the moon and thinking for no reason.";
file.Seek(0, FILE_END);
file.Write(buf, strlen(buf));
file.Flush();
return 0;
}
Linux file operations
Stay tuned