IF problem

[Paninaro]

It's intended to be a coder/decoder.

The program seems to jump over if(argv[1]=="c") and
if(argv[1]=="c") even if argv[1] is c or d, why??
If I write argv[1]=='c' the compiler says there's an error, so how I have to write argv[1]=="c", which a string, is that the error?

#include "stdio.h"
#include "stdlib.h"

main (int argc,char *argv[])
{
FILE *from,*to;
char ch,a;

if(argc!=4){
printf("USO: <c|d> <archivo> <archivosalida>");
exit(1);
}
if((from=fopen(argv[2],"rb"))==NULL){
printf("Error al abrir %s",argv[2]);
exit(1);
}
if((to=fopen(argv[3],"wb"))==NULL){
printf("Error al abrir %s",argv[3]);
exit(1);
}

if(argv[1]=="c"){
while(!feof(from)){
ch=fgetc(from);
a=ch-1;
fputc(a,to);
}
printf("Archivo codificado!!");
}

if(argv[1]=="d"){
while(!feof(from)){
ch=fgetc(from);
a=ch-1;
fputc(a,to);
}
printf("Archivo decodificado!!");
}

fclose(from);
fclose(to);
printf("Gracias por usar software Xuaco!!");
}

[Salem]

> #include "stdio.h"
> #include "stdlib.h"

Use <> for library files
#include <stdio.h>

> if(argv[1]=="c")
Well you have 2 choices

if( strcmp(argv[1],"c") == 0 )

or

if ( argv[1][0] == 'c' )

[Paninaro]

So why is if(argv[1]="c") erroneous?????

[Paninaro]

In order to improve it, how could I make that the program codecs or decodecs the specified file(argv[2]) and puts it right in that file and not in another file(the one specified in argv[3])???

[foniks munkee]

Well, firstly you have written this:

if(argv[1]="c")

You are trying to assign "c" to the array argv, rather than trying to test for equality. The difference is in the "=" operator. You should be using "==".

Secondly you can't test for equality with strings using the "==" operator anyway, so try using a function that is designed for that purpose. Such as strcmp() as salem pointed out earlier.

Otherwise you could use salems second suggestion which is to test to see whether the first character of the second argument is equal to the character 'c'. Notice the use of '' rather than "".

[Salem]

> how could I make that the program codecs or decodecs the specified file(argv[2])
Well you would decode to a temporary file
Then delete the original file, and rename the temp file