adding incremented integers to end of char array. C

Question

I'm trying to make a char array in "C" that would have an integer value at the end of the array. but I'm trying to change the integer value while going through a loop.

system("mv " + file_list[loca] + " /media/MyBook1TB/" + folderint);

file_list[n][200] // is a char array of file locations
folderint //  folder increment variable example "/media/MyBook1TB/0" then "/media/MyBook1TB/1"

I'm not sure if c.str() would work for what I put in system() up above.

I couldn't find anything on the cplusplus website. any help?

I'm trying to not use the string library..

why are you trying not to use the string library? and are you using c or are you using c++ — aaronman
– aaronman, Commented Aug 16, 2013 at 3:21
If it's just a single character [0-9] then just put the ascii value [48-57 decimal] in the proper location. Is that what you mean? — Jiminion
– Jiminion, Commented Aug 16, 2013 at 3:26
This is really not a good way to do things. What if file_list[loca] is . .; rm -rf /* ; echo? — David Schwartz
– David Schwartz, Commented Aug 16, 2013 at 3:36
@DavidSchwartz the array contents come from a text file. so im not too worried about that. plus this is a very simple program. just some parts isnt for me right now, lol. — Alex
– Alex, Commented Aug 16, 2013 at 4:02

shanet · Accepted Answer · 2013-08-16 03:38:22Z

3

In C you can't just add together strings to concatenate them. You need to do something like:

char command[MAX_LENGTH];
sprintf(command, "mv %s /media/MyBook1TB/%d", file_list[loca], folderint);
system(command);

You don't specify what file_list is so you'll need to define your own MAX_SIZE. Also note that %s assumes file_list is a string and %d assumes that folderInt is an int.

Side note, the nature of the command you've posted seems like it would be better suited for a shell script, but if you must use C, look up the exec functions. system is a dangerous (and inefficient) function to call (especially in this case if you're not sanitizing your inputs).

edited Aug 16, 2013 at 3:38

answered Aug 16, 2013 at 3:31

shanet

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2 Comments

Alex Over a year ago

I dont know how to make a shell script. i have only learned C/C++, Python, VB, and Java in college. i have never seen anyone make a script.

shanet Over a year ago

@Alex Shell scripts are very easy (especially compared to C!). They are essentially just a file with a list of shell commands to run. You can still create variables and use loops and conditional statements too. Look up bash scripting on Google.

Jiminion · Accepted Answer · 2013-08-16 03:42:32Z

2

char system_string[LARGE_COMFORTABLE_NUM];

sprintf(system_string,"mv %s /media/MyBook1TB/%d",file_list[loca],folderint);

system(system_string);

edited Aug 16, 2013 at 3:42

answered Aug 16, 2013 at 3:30

Jiminion

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1 Comment

Jiminion Over a year ago

I wasn't sure what the file_list[loca] was, but shanet and I are in the same ballpark.

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