rename C Library Function

The function int rename(const char *oldName, const char *newName); changes the name of the file specified by oldName to newName. It directly renames the file identified by the oldName without any stream operation. If a file with name newName already exists, the rename function may either override the existing file or fail, depending on the implementation.

Function prototype of rename

int rename(const char *oldName, const char *newName);

• oldName : This is a null terminated string containing the name of an existing file to be renamed.
• newName : This is a null terminated string containing the new name of the file.

Return value of rename

On Success, rename function returns zero otherwise in case of an error it returns -1 and sets errno variable to a system-specific error code.

C program to using rename function

The following program shows the use of rename function to rename an exiting file. Below program first creates a file called textFile.txt and then renames it to newTestFile.txt using rename function.

#include <stdio.h>
 
int main (){
   int response;
   FILE *file;
    
   /* Create a new file */
   file = fopen("textFile.txt", "w");
   fputs("TechCrashCourse.com", file);
   fclose(file);
    
   /* Rename textFile.txt to newTextFile.txt */
   response = rename("textFile.txt", "newTextFile.txt");
 
   if(response == 0) {
      printf("textFile.txt renamed to newTextFile.txt\n");
   } else {
      printf("Error: unable to rename textFile.txt");
   }
    
   return(0);
}

Output

textFile.txt renamed to newTextFile.txt