C - UNIX commands in program

Question

I'm trying to create a program where it would count the number of directories, or the number of readable/writable/executable files. The user would input only the name of the author and the letters "d", "r", "w", or "x". I tried to directly call "ls -l" in my program but that caused an error. How do you call UNIX commands within a C program?

Although system() 'works', you'd have to manufacture the command line carefully; there's no way for the launching program to filter the output (in the ordinary course of events). You might need to use POSIX functions popen(), or maybe fork() and execvp() and related functions (pipe(), dup2(), …). — Jonathan Leffler
– Jonathan Leffler, Commented Jan 27, 2016 at 3:41
You might also want to investigate POSIX functions nftw(), opendir(), readdir(), stat(). — Jonathan Leffler
– Jonathan Leffler, Commented Jan 27, 2016 at 3:43

tdao · Accepted Answer · 2016-01-27 03:13:06Z

1

I tried to directly call "ls -l" in my program but that caused an error. How do you call UNIX commands within a C program?

You can se system in your C program, for example:

system( "ls -l" );

For that to work, you'll also need to #include <stdlib.h>

answered Jan 27, 2016 at 3:13

tdao

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2 Comments

Dietrich Epp Over a year ago

I think the program output is necessary in this case too.

Stack Exchange Broke The Law Over a year ago

In that case use popen

Scott Sosna · Accepted Answer · 2016-01-27 03:14:39Z

0

Using the find command might work better, you could count directories with the command "find . -t d | wc -l" and do something similar for files with the appropriate flags.

answered Jan 27, 2016 at 3:14

Scott Sosna

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