用标准C实现shell功能

　　#include

#include

#include

#include

#include

#include

#define SHELL_NAME "sh1"

#define PROMPT_ENVIRONMENT_VARIABLE "PROMPT"

char *prompt;

int main(int argc, char **argv)

{

char cmd[80];

int statval;

/* Determine prompt value. */

if ((prompt = getenv(PROMPT_ENVIRONMENT_VARIABLE)) == NULL)

prompt = SHELL_NAME ":";

/* Process commands until exit, or death by signal. */

while (1)

{

/* Prompt and read a command. */

printf(prompt);

gets(cmd);

/* Process built-in commands. */

if(strcasecmp(cmd, "exit") == 0)

break;

/* Process non-built-in commands. */

if(fork() == 0) {

execlp(cmd, cmd, NULL);

fprintf(stderr, "%s: Exec %s failed: %s

", argv[0],

cmd, strerror(errno));

exit(1);

}

wait(&statval);

if(WIFEXITED(statval))

{

if(WEXITSTATUS(statval))

{

fprintf(stderr,

"%s: child exited with status %d.

",

argv[0], WEXITSTATUS(statval));

}

} else {

fprintf(stderr, "%s: child died uneXPectedly.

",

argv[0]);

}

}

}