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#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int, char**);
void color_settopaper();
void color_revert();
void newline();
void done(int);
void stripnl(char *);
void color_warning();
void help();
int usecolor = 1;

//usage "peek <file> -m <linecount> --nocolor

//BEGIN ACTUALL CODE
int main(int argc, char** argv) {
	//defaults and declarations
//	int usecolor = 1;
	int maxcount = 10; 
	int lcount = 0;
	if (argc==1) {done(1);}
	//parse the arguments...
	int i=0;
	
	for (i=2;i<=argc;i++) {
		if (!strcmp(argv[i],"-m")) {
			maxcount = atoi(argv[(i+1)]);
			i++;
			continue;
		}
		if (!strcmp(argv[i],"--nocolor")) {
			usecolor = 0;
			continue;
		}
		if (!strcmp(argv[i],"-l")) {
			lcount = atoi(argv[(i+1)]);
			i++;
			continue;
		}
		if (!strcmp(argv[i],"--help")) {
			help();
			continue;
		}
		color_warning();
		printf("You passed me an invalid switch: %s. I'll ignore it this time but ",argv[i]);
		color_error();
		printf("DON'T LET IT HAPPEN AGAIN!");
		color_revert();
		printf(" Thanks!");
		newline();
	}

	color_settopaper();
	FILE *infile;
	char line[100];
	/* Read in the filename */
	/* We need to get rid of the newline char. */
	stripnl(argv[1]);
	/* Open the file.  If NULL is returned there was an error */
	if((infile = fopen(argv[1], "r")) == NULL) {
		done(2);
	}
  
	while(fgets(line, sizeof(line), infile) != NULL || lcount>maxcount) {
		/* Get each line from the infile */
		lcount++;
		/* print the line number and data */
		printf("Line %d: %s", lcount, line);  
  	}
 
	fclose(infile);  /* Close the file */

	color_revert();
	done(0); //finish with no error
}

void stripnl(char *str) {
  while(strlen(str) && ( (str[strlen(str) - 1] == 13) || 
       ( str[strlen(str) - 1] == 10 ))) {
    str[strlen(str) - 1] = 0;
  }
}
void color_warning() {
	printf("\033[31;42m");
}
void color_settopaper() {
	if (usecolor) printf("\033[30;47m");
}
	
void color_revert() {
	if (usecolor) printf("\033[0m");
}

void color_error() {
	if (usecolor) printf("\033[1;33;41m");
}
void newline() {
	printf("\n");
}
void help() {
	printf("Let colors be enabled if possible for this help message");
	newline();
	printf("Peek allows you to peek at a file without seeing the entire thing");
	newline();
	printf("Peek does not clear the entire screen");
	newline();
	printf("Usage:");
	newline();
	printf("	peek <filename> [-m <numberoflines> -l <startingline> --nocolor --help");
	newline();
	printf("You MUST specify a file name to peek at!");
	newline();
	printf("Options:");
	newline();
	printf("-m <numberoflines>	<numberoflines> specifies how many lines to peek at. The default is 10.");
	newline();
	printf("-l <startingline>	<startingline> specifies where to start in the file. The default is at the begining.");
	newline();
	printf("--nocolor		Disables the use of color in the program's output.");
	newline();
	printf("--help			Displays this help file and quits.");
	newline();
	printf("If you pass the program an invalid switch, it may be rude about it.");
	newline();
	newline();
	color_settopaper();
	printf("This color");
	color_revert();
	printf(" is the \"paper\" color. The file will be this color");
	newline();
	color_warning();
	printf("This color");
	color_revert();
	printf(" is a warning color; not used often.");
	newline();
	color_error();
	printf("This color");
	color_revert();
	printf(" is the error color.");
	done(0);
}
void done(int errorcode) {
	if (errorcode==1) {
		color_error();
		printf("No file specified. Please specify a file.");
	}
	if (errorcode==2) {
		color_error();
		printf("Error opening the file specified. Make sure the source is readable");
	}
	color_revert();
	printf("\n");
	exit(1);
}

Code: Select all

[root@localhost peek]# ./a.out
No file specified. Please specify a file.
[root@localhost peek]# ./a.out foo.bar 
Segmentation fault
[root@localhost peek]# ./a.out foo.bar -m 7
Segmentation fault

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[root@localhost peek]# gdb a.out
GNU gdb (GDB) Red Hat Enterprise Linux (7.0.1-37.el5_7.1)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i386-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /root/programs/peek/a.out...(no debugging symbols found)...done.
(gdb) run
Starting program: /root/programs/peek/a.out 
No file specified. Please specify a file.

Program exited with code 01.
(gdb) ru foo.dat
Starting program: /root/programs/peek/a.out foo.dat

Program received signal SIGSEGV, Segmentation fault.
0x08048894 in main ()
(gdb) backtrace
#0  0x08048894 in main ()

Code: Select all

if (!strcmp(argv[i],"-m")) {

Code: Select all

for (i=2;i<=argc;i++)