C Programming Code Examples
C > File Operations Code Examples
C Program to Join Lines of Two given Files and Store them in a New file
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/* C Program to Join Lines of Two given Files and Store them in a New file */
#include <stdio.h>
#include <stdlib.h>
/* Function Prototype */
int joinfiles(FILE *, FILE *, FILE *);
char ch;
int flag;
void main(int argc, char *argv[])
{
FILE *file1, *file2, *target;
file1 = fopen(argv[1], "r");
if (file1 == NULL)
{
perror("Error Occured!");
}
file2 = fopen(argv[2], "r");
if (file2 == NULL)
{
perror("Error Occured!");
}
target = fopen(argv[3], "a");
if (target == NULL)
{
perror("Error Occured!");
}
joinfiles(file1, file2, target); /* Calling Function */
if (flag == 1)
{
printf("The files have been successfully concatenated\n");
}
}
/* Code join the two given files line by line into a new file */
int joinfiles(FILE *file1, FILE *file2, FILE *target)
{
while ((fgetc(file1) != EOF) || (fgetc(file2) != EOF))
{
fseek(file1, -1, 1);
while ((ch = fgetc(file1)) != '\n')
{
if (ch == EOF)
{
break;
}
else
{
fputc(ch, target);
}
}
while ((ch = fgetc(file2)) != '\n')
{
if (ch == EOF)
{
break;
}
else
{
fputc(ch, target);
}
}
fputc('\n', target);
}
fclose(file1);
fclose(file2);
fclose(target);
return flag = 1;
}
The break is a keyword in C which is used to bring the program control out of the loop. The break statement is used inside loops or switch statement. The break statement breaks the loop one by one, i.e., in the case of nested loops, it breaks the inner loop first and then proceeds to outer loops.
Close file. Closes the file associated with the stream and disassociates it. All internal buffers associated with the stream are disassociated from it and flushed: the content of any unwritten output buffer is written and the content of any unread input buffer is discarded. Even if the call fails, the stream passed as parameter will no longer be associated with the file nor its buffers.
Get character from stream. Returns the character currently pointed by the internal file position indicator of the specified stream. The internal file position indicator is then advanced to the next character. If the stream is at the end-of-file when called, the function returns EOF and sets the end-of-file indicator for the stream (feof). If a read error occurs, the function returns EOF and sets the error indicator for the stream (ferror). getc and fgetc are equivalent, except that getc may be implemented as a macro in some libraries. See getchar for a similar function that reads directly from stdin.
Write character to stream. Writes a character to the stream and advances the position indicator. The character is written at the position indicated by the internal position indicator of the stream, which is then automatically advanced by one. putc and fputc are equivalent, except that putc may be implemented as a macro in some libraries. See putchar for a similar function that writes directly to stdout.
The open() function shall establish the connection between a file and a file descriptor. It shall create an open file description that refers to a file and a file descriptor that refers to that open file description. The file descriptor is used by other I/O functions to refer to that file. The path argument points to a pathname naming the file. The open() function shall return a file descriptor for the named file that is the lowest file descriptor not currently open for that process. The open file description is new, and therefore the file descriptor shall not share it with any other process in the system. The FD_CLOEXEC file descriptor flag associated with the new file descriptor shall be cleared.
Get character from stream. Returns the character currently pointed by the internal file position indicator of the specified stream. The internal file position indicator is then advanced to the next character. If the stream is at the end-of-file when called, the function returns EOF and sets the end-of-file indicator for the stream (feof). If a read error occurs, the function returns EOF and sets the error indicator for the stream (ferror). fgetc and getc are equivalent, except that getc may be implemented as a macro in some libraries.
Print error message. Interprets the value of errno as an error message, and prints it to stderr (the standard error output stream, usually the console), optionally preceding it with the custom message specified in str. errno is an integral variable whose value describes the error condition or diagnostic information produced by a call to a library function (any function of the C standard library may set a value for errno, even if not explicitly specified in this reference, and even if no error happened), see errno for more info.
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Reposition stream position indicator. Sets the position indicator associated with the stream to a new position. For streams open in binary mode, the new position is defined by adding offset to a reference position specified by origin. For streams open in text mode, offset shall either be zero or a value returned by a previous call to ftell, and origin shall necessarily be SEEK_SET. If the function is called with other values for these arguments, support depends on the particular system and library implementation (non-portable). The end-of-file internal indicator of the stream is cleared after a successful call to this function, and all effects from previous calls to ungetc on this stream are dropped.
Closes a file descriptor, fildes. This frees the file descriptor to be returned by future open() calls and other calls that create file descriptors. The fildes argument must represent a hierarchical file system (HFS) file. When the last open file descriptor for a file is closed, the file itself is closed. If the file's link count is 0 at that time, its space is freed and the file becomes inaccessible. When the last open file descriptor for a pipe or FIFO file is closed, any data remaining in the pipe or FIFO file is discarded. close() unlocks (removes) all outstanding record locks that a process has on the associated file. Behavior for sockets: close() call shuts down the socket associated with the socket descriptor socket, and frees resources allocated to the socket. If socket refers to an open TCP connection, the connection is closed. If a stream socket is closed when there is input data queued, the TCP connection is reset rather than being cleanly closed.
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