手把手教你編寫一個具有基本功能的shell（已開源）
阿新 • • 發佈：2018-12-21
/*read command line until EOF*/while(read(stdin,buffer,numchars)){ /*parse command line*/ if(/* command line contains & */) amper = 1; else amper = 0; /* for commands not part of the shell command language */ if(fork() == 0) { /* redirection of IO?*/ if(/* redirect output*/) { fd = creat(newfile,fmask); close(stdout); dup(fd); close(fd); /* stdout is now redirected */ } if(/* piping */) { pipe(fildes); if(fork() == 0) { /* first component of command line*/ close(stdout); dup(fildes[1]); close(fildes[1]); close(fildes[0]); /* stdout now goes to pipe */ /* child process does command */ execlp(command1,command1,0); } /* 2nd command component of command line*/ close(stdin); dup(fildes[0]); close(fildes[0]); close(fildes[1]); /* standard input now comes from pipe */ } execve(command2,command2,0); } /* parent continues over here ... /* waits for child to exit if required */ if(amper == 0) retid = wait(&status);}