C language——to Replace a specified Line in a Text File

C language——to Replace a specified Line in a Text File—V2

[root@localhost 桌面]# gedit tmp.c

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// C Language to Replace a specified Line in a Text File
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//filename: "/etc/hosts"
//str: "mpe.localhost"
//return the matched line number
int findline(char *filename, char *str)
{
// open the file for reading
FILE *file = fopen(filename, "r");
// make sure the file opened properly
if(NULL == file)
{
fprintf(stderr, "Cannot open file: %s ", filename);
return 1;
}
// set up the buffer to read the line into. Don't worry too much
// if some of the lines are longer than 80 characters - the buffer
// will be made bigger if need be.
size_t buffer_size = 80;
char *buffer = malloc(buffer_size * sizeof(char));
// read each line and print it to the screen
int line_number = 0, find = 0;
while(-1 != getline(&buffer, &buffer_size, file))
{
line_number++;
if(NULL != strstr(buffer, str))
{
find = 1;
break;
}
//printf("%d: %s", line_number, buffer);
}
if(find == 0) line_number = 0;
fclose(file);
free(buffer);
return line_number;
}
void replaceline(char *filename, int delete_line, char *newcontent)
{
FILE *fileptr1, *fileptr2;
//char filename[40];
char c;
int temp = 1;
fileptr1 = fopen(filename, "r");
//print the contents of file .
while ((c = getc(fileptr1)) != EOF)
{
printf("%c", c);
}
//take fileptr1 to start point.
rewind(fileptr1);
//open tempinterm.txt in write mode
fileptr2 = fopen("tempinterm.txt", "w");
while ((c = getc(fileptr1)) != EOF)
{
//till the line to be deleted comes,copy the content to other
if (temp != delete_line) {
putc(c, fileptr2);
while ((c = getc(fileptr1)) != 'n') putc(c, fileptr2);
putc('n', fileptr2);
temp++;
} else {
while ((c = getc(fileptr1)) != 'n'); //read and skip the line
//while ((c = getchar()) != 'n') putc(c, fileptr2);
while(*newcontent != '0') putc(*newcontent++, fileptr2);
putc('n', fileptr2);
temp++;
}
}
//append a new line at the end of file
if(delete_line == 0)
{
while(*newcontent != '0') putc(*newcontent++, fileptr2);
putc('n', fileptr2);
}
fclose(fileptr1);
fclose(fileptr2);
remove(filename);
rename("tempinterm.txt", filename);
}
int main(void)
{
FILE *fileptr1;
char c;
char filename[6] = "hosts";
int line = findline(filename, "mpe.localhost");
replaceline(filename, line, "10.108.162.227 mpe.localhost");
fileptr1 = fopen(filename, "r");
//reads the character from file
//until last character of file is encountered
while ((c = getc(fileptr1)) != EOF) printf("%c", c);
fclose(fileptr1);
return 0;
}

[root@localhost 桌面]# gcc tmp.c -o tmp
[root@localhost 桌面]# ./tmp
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
10.108.162.227   mpe.localhost
[root@localhost 桌面]#

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