sort:multi-character tab in C error - c

Question

I have error multi-character tab ` \' \' -k 10 -r -n log.txt'
int
main ()
{
const char *sort[] = { "sort", "-t ' ' -k 10 -r -n log.txt", 0 };
const char *awk[] = { "awk", "{print $10}", 0 };
struct command cmd [] = { {sort}, {awk} };
return fork_pipes (2, cmd);
}
How backspace escape or correct sort argument in C.
All code:
#include <unistd.h>
struct command
{
const char **argv;
};
int
spawn_proc (int in, int out, struct command *cmd)
{
pid_t pid;
if ((pid = fork ()) == 0)
{
if (in != 0)
{
dup2 (in, 0);
close (in);
}
if (out != 1)
{
dup2 (out, 1);
close (out);
}
return execvp (cmd->argv [0], (char * const *)cmd->argv);
}
return pid;
}
int
fork_pipes (int n, struct command *cmd)
{
int i;
pid_t pid;
int in, fd [2];
/* The first process should get its input from the original file descriptor 0. */
in = 0;
/* Note the loop bound, we spawn here all, but the last stage of the pipeline. */
for (i = 0; i < n - 1; ++i)
{
pipe (fd);
/* f [1] is the write end of the pipe, we carry `in` from the prev iteration. */
spawn_proc (in, fd [1], cmd + i);
/* No need for the write and of the pipe, the child will write here. */
close (fd [1]);
/* Keep the read end of the pipe, the next child will read from there. */
in = fd [0];
}
/* Last stage of the pipeline - set stdin be the read end of the previous pipe
and output to the original file descriptor 1. */
if (in != 0)
dup2 (in, 0);
/* Execute the last stage with the current process. */
return execvp (cmd [i].argv [0], (char * const *)cmd [i].argv);
}
int
main ()
{
const char *sort[] = { "sort", "-t ' ' -k 10 -r -n log.txt", 0 };
const char *awk[] = { "awk", "{print $10}", 0 };
struct command cmd [] = { {sort}, {awk} };
return fork_pipes (2, cmd);
}

Answer 1

I assume that the strings are passed as arguments to one of the exec functions? Then you can't put multiple arguments in a single string because exec will treat it as a single argument to the program.
The arguments to exec is what becomes the argv array in the called program, so for example "-t ' ' -k 10 -r -n log.txt" will become a single argument (e.g. argv[1]) in the called program. You need to separate the arguments:
const char *sort[] = { "sort", "-t", " ", "-k", "10", "-r", "-n", "log.txt", 0 };