无法读取bash行生成的文件

Question

I have written a C code where the bash script lines are used inside this C code, and this is how I wrote it:

printf("wc -l < smallerthan > number_lines\n");   
if( (fr=fopen(fname_rcut,"r"))==NULL )  {  printf("error in rcut file:   %s\n",fname_rcut);  exit(1);  }  

I need to read the file "number_lines" which is generated from "smallerthan" file, the problem is when I source the C code to run automatically like:

$gcc myC_code.c -lm     
$./a.out > run.sh  
$source run.sh   

Then if I view the run.sh

& vi run.sh 

I get this inside run.sh :

    wc -l < smallerthan > number_lines  
    ls 

    error in rcut file: /home/number_lines

which mean the code upto this point didn't find my "number_lines" file yet since the number_lines file is yet to appear, but if I copy the line and run it separately, instead of "automatically", then it works because the file is there now.

My question is, how to make my code run automatically and my C code to read the file which is generated by bash line or how to generate the file and read it properly?

Any idea please because I'm really new to programming and I have to use bash inside C for my work.

Note: the above is only small part of my C code but I used several bash lines inside my C code.

Answer 1

There are a number of observations in your code. I assume that char *fname_rcut indeed points to "/home/number_lines" .

First observation: if you write commands to a file, they will not be executed.So the file number_lines is created only after you run run.sh . Therefore, the file will not exist during the execution of your C program. You might look into int system(const char *command) ( man 3 system ).

Second observation: /home/number_lines is probably not the correct filename. It would probably be /home/your_name/number_lines ; try a pwd to see what the exact directory name is.

Third observation: Why do you want to source run.sh ? Source executes the file in the current shell. There is usually no need for that.

Answer 2

I have solved it :
what we need actually is using system(command) after each shell command
for example :

printf("wc -l < smallerthan > number_lines\n");     

will be after solving :

sprintf(command1,"wc -l < smallerthan > number_lines\n");  
system(command1);