1 files changed, 90 insertions, 0 deletions
diff --git a/replace.c b/replace.c
new file mode 100644
index 0000000..d9a0157
--- /dev/null
+++ b/replace.c
@@ -0,0 +1,90 @@
+/*
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+size_t
+getfilelength(FILE *fp)
+{
+	/* 
+	 * return the number of bytes in file fp	
+    	 * value of 0 returned is empty or error
+	 * it doesn't matter for our purpose
+	 */
+	size_t retval;
+	if (!fp)
+		retval = 0;
+	else
+	{
+		fseek(fp, 0, SEEK_END);
+		retval = ftell(fp);
+		fseek(fp, 0, SEEK_SET);
+	}
+	return retval;
+}
+
+void
+appendchar(char *dest, char ch)
+{
+	int len = strlen(dest);
+	dest[len] = ch;
+	dest[len+1] = '\0';
+}
+
+int
+replaceinfile(char *originalfile, char *destinationfile, char *placeholder, char *replacement)
+{
+	/*
+	 * write originalfile into destinationfile replacing every instance 
+	 * of placeholder with replacement 
+	 */
+
+	/* open files */
+	FILE *template = fopen(originalfile, "r");
+	FILE *destination = fopen(destinationfile, "w");
+	if (!template)
+	{
+		fclose(destination);
+		return 0;
+	}
+	int ch;
+	char *substr;
+	size_t filesize = getfilelength(template);
+	char *filebuffer = malloc(filesize+1);
+	if (!filebuffer)
+		return 0;
+	fread(filebuffer, 1, filesize, template);
+	substr = strstr(filebuffer, placeholder);
+	for (size_t i = 0; i < strlen(filebuffer); i++)
+	{
+		if (i == (substr-filebuffer))
+		{
+			i += strlen(placeholder);
+			substr++;
+			substr = strstr(substr, placeholder);
+			printf("%s", replacement);
+			fprintf(destination, "%s", replacement);
+		}
+		ch = filebuffer[i];
+		putchar(ch);
+		fputc(ch, destination);
+	}
+	fclose(template);
+	fclose(destination);
+	free(filebuffer);
+	return 1;
+}