Modifing global array of strings from function C

Question

I having trouble debugging the folowing code I want to get all items in the hisory from processHIstory() functioon but i am getting undesired result

here is what i am tring to do assume user enters the folowong ...

>> ls
>> pwd
>> clear

then history array will be

histrory= {"ls","pwd","clear"}

and when user wants history like this

 >>!!

I need all histories to displaylike

ls 
pwd
clear

but I am getiing the folowing now

 !!
 !!
 !!

what is my problem?please help me.

Here is the git link to my code! GIST

thank you.

@zenith from processhistory() function the result are (null)(null)(null) when displayed! — m_Et
– m_Et, Commented Feb 7, 2015 at 4:46

ilent2 · Accepted Answer · 2015-02-07 12:49:45Z

2

I suspect when you do history[commandsExcuted]=argv[0]; you then go and change the value of argv[0] which is a pointer.

What you need to do is allocate memory for the string and copy it into history, perhaps something like:

history[commandsExecuted] = malloc(strlen(argv[0]));
strcpy(history[commandsExecuted], argv[0]);

Sorry if this doesn't compile, its been a while since I have worked with C/malloc/str* functions. So much nicer in C++.

Edit: Instead of manually calling malloc and strcpy there is also strdup, from the man page:

The strdup() function returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with malloc(3), and can be freed with free(3).

edited Feb 7, 2015 at 12:49

answered Feb 7, 2015 at 4:42

ilent2

5,2513 gold badges23 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

m_Et Over a year ago

I am getting null form out put ... when processhistory() is called

m_Et Over a year ago

@zenith do you try it with my code, it's not working for me, which line do you modify.

flogram_dev Over a year ago

I copypasted your code, replaced history[commandsExcuted]=argv[0]; in processCommand with the two lines ilent2 proposed, and the history is now showing correctly to me.

Collectives™ on Stack Overflow

Modifing global array of strings from function C

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related