Login or Register to Ask a Question and Join Our Community


Programming

help with C, argv

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Programming help with C, argv
# 1  
Old 02-08-2011
Error help with C, argv
when i run my program, i have a parameter, that i want to set the value to another string

i am using
Code:
int main(int argc, char **argv) {

    char my_str=argv[2];
    printf("%s",my_str);

   return 0;
}

and i get
Segmentation fault

ran using
Code:
./my_prog /usr/share/dict/words hello1

but this isnt working, does anyone know why?
Last edited by Scott; 02-09-2011 at 10:17 AM.. Reason: Code tags, please...
# 2  
Old 02-09-2011
your passing the wrong type to printf. you need to pass a pointer to a string and your currently passing a char or really a int since char is typedef; enable warnings when compiling eg: gcc -Wall. also add #include <stdio.h> at the top of your source file

Code:
char *my_str=argv[2];

also - please use code tags.
# 3  
Old 02-09-2011
Or, to further an explanation, what a string really is, is a pointer to memory, telling where the string is stored. You can't store it in a single character. When printf() expects a pointer and you hand it a character, it goes to whatever garbled value got stored in your char and tries to read it, and since it's almost certainly invalid, crashes.
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

ARGV how to use it?

So i am trying to read in file readFile <GivenFile> modFile looking for a regular file under the directories in the GivenFile and print them out is my over all goal. basically I am looking for anything that looks like a directory in the given file and printing it out. Since I am trying to do... (2 Replies)
Discussion started by: squidGreen
2 Replies

2. UNIX for Advanced & Expert Users

O argv, argv, wherefore art thou argv?

All of my machines (various open source derivatives on x86 and amd64) store argv above the stack (at a higher memory address). I am curious to learn if any systems store argv below the stack (at a lower memory address). I am particularly interested in proprietary Unices, such as Solaris, HP-UX,... (9 Replies)
Discussion started by: alister
9 Replies

3. Programming

How do I copy or rewind *argv[]

I'm working on my own pow function and I need to make a copy of *argv but I think that I am having trouble with the size of *argv and the size of any array that I make. The code below isn't working for me. and I want to accept any number no matter the size with pow -f 2 2. I was working out... (16 Replies)
Discussion started by: Errigour
16 Replies

4. Programming

ARGV help in C

Hi, Can somehelp help how to list file in a dir? (5 Replies)
Discussion started by: Learnerabc
5 Replies

5. Shell Programming and Scripting

$#Argv in Csh

Hello all, Had a quick question: In a typical csh script should inputting via stdin (i.e. set i = $< ) increase the value of $#argv ? echo enter an value: set val= "$<" if($#argv == 0) then echo No args else echo The arg is $argv so if a value is inputted #argv... (1 Reply)
Discussion started by: new2C
1 Replies

6. Shell Programming and Scripting

if #argv = (this OR that) then...

this is in one of my scripts... if ($#argv == 0) then echo 'blah bla' exit 0 endif I want it to be something like this... if ($#argv == 0 OR $argv >=3) echo 'blah bla' exit 0 endif so when the arguments are none, or greater than three I want this "if then" to take over. how? I... (5 Replies)
Discussion started by: ajp7701
5 Replies

7. Programming

help for argv argc

Hi C experts, I have the following code for adding command line option for a program int main (argc, argv) int argc; char *argv; { char *mem_type; //memory type char *name; //name of the memory int addr; //address bits int data; ... (5 Replies)
Discussion started by: return_user
5 Replies

8. Shell Programming and Scripting

Perl: Getting $ARGV's to operate like while(<>)

I have a script that asks a bunch of questions using the following method for input: print "Name:"; while(<>){ chomp; $name=$_; } So for example, if the questions asked for name, age, & color (in that order)... I want to be able to easily convert $ARGV into the input expected by... (2 Replies)
Discussion started by: jjinno
2 Replies

9. Programming

Using argv argc

I searched on the forums. No advises. I am using a previous source code. I changed the main function main(int argc, char **argv) in a function misc(int argc, char **argv). How do you use the argc and argv parameters? This is how I am calling the function : char param; strcat(param,"wgrib ");... (4 Replies)
Discussion started by: Akeson Chihiro
4 Replies

10. Programming

argv

I have a program which I wish to modify. It used to be run from the command line, but now I wish to change this so it can be used as a function. The program has complex argument processing so I want to pass my paramters to as if it were being called by the OS as a program. I have tried to... (2 Replies)
Discussion started by: mbb
2 Replies
Login or Register to Ask a Question