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copied!<p>The problem is, you do allocate a char* array inside <code>parse_command</code>, but the pointer to that array never gets out of the function. So <code>exec_command</code> gets a garbage pointer value. The reason is, by calling <code>parse_command(line, command)</code> you pass <em>a copy of the current value</em> of the pointer <code>command</code>, which is then overwritten inside the function - but <em>the original value is not affected by this!</em></p> <p>To achieve that, either you need to pass <em>a pointer to</em> the pointer you want to update, or you need to return the pointer to the allocated array from <code>parse_command</code>. Apart from <code>char***</code> looking ugly (at least to me), the latter approach is simpler and easier to read:</p> <pre><code>int main() { char** command = NULL; while (true) { fgets(line, MAX_COMMAND_LEN, stdin); command = parse_command(line); exec_command(command); } } char** parse_command(char* line) { char** command = NULL; int n_args = 0, i = 0; while (line[i] != '\n') { if (isspace(line[i++])) n_args++; } command = (char**) malloc ((n_args + 1) * sizeof(char*)); i = 0; line = strtok(line," \n"); while (line != NULL) { command[i] = (char *) malloc ( (strlen(line)+1) * sizeof(char) ); strcpy(command[i++], line); line = strtok(NULL, " \n"); } command[i] = NULL; return command; } </code></pre> <p>Notes:</p> <ul> <li>in your original <code>parse_command</code>, you allocate memory to <code>command</code> in a loop, which is unnecessary and just creates memory leaks. It is enough to allocate memory once. I assume that you want <code>command</code> to contain <code>n_args + 1</code> pointers, so I modified the code accordingly.</li> <li>in the last <code>while</code> loop of <code>parse_command</code>, you increment <code>i</code> incorrectly twice, which also leads to undefined behaviour, i.e. possible segmentation fault. I fixed it here.</li> </ul>

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