簡單shell 命令重新導向

今天晚上花了一會寫的，開始用的是 argv 是個二位元組， 調程式的時候總是顯示不出，後來發現execvp貌似只支援 pointer array =。= 好吧。。。。
程式思路：開子進程以後把 子進程的標準輸出 關閉， 然後在子進程中建立一個檔案，此時檔案會選擇 自身進程中最小的檔案標識符 作為該檔案的檔案標識符,也就是fd

所以，以後子進程的所有標準輸出都流向了檔案， 這個應該是簡單的思路了吧，感覺GNU的源碼應該是用無名管道，甚至是有名管道（網路傳輸） 實現的，好吧我就不意淫了。。。 有興趣的朋友可以去官網上找找 GNU/Linux 的shell 原始碼

/*  1.c *  author:wangshiyang *  date: 2013/5/13 */#include <stdio.h>#include <unistd.h>#include <string.h>//------------------------------------------------------/* for the convience I'v set a lot of global-variables | * the formal shell program may not dit like this   | * */// warning: use argv[][] is wrong !!!  |char input[100];// the command you input               |char *argv[30];//the execvp must use point array   |char file[100];//you can input a filename              |//------------------------------------------------------char *newstr( char *s, int l ){char * rv = (char *)malloc( l+1 );rv[l] = '\0';strncpy( rv, s, l);return rv;}int deal()// deal the input command{char temp[100];int len, i, a, turn;fgets(input, 100, stdin);len = strlen(input);turn = 0; a = 0; for( i = 0; i < len; i++ ){if( input[i] == '\n' ){argv[turn++] = newstr( temp, strlen(temp) );break;}if( input[i] != ' ' ){temp[a++] = input[i];temp[a] = '\0';}else{argv[turn++] = newstr( temp, strlen(temp) );a = 0;}}for( i = 0; i < turn; i++ )if( !strcmp( argv[i], ">" )){strcpy( file, argv[i+1]);//copy the filename to file arrayreturn i;}return -1;};void execute( int flag )// run the command {intpid, fd;argv[flag] = NULL;if( (pid = fork() ) == -1 ){perror( "fork" ); exit(1);}if ( pid == 0 ){/* 0 for stdin, 1 for stdout, 2 for stderr */close(1);// close the stdout fd = creat( file, 0777 );// then open and fd connect to 1execvp( argv[0], argv );// and runperror( "execvp" );exit(1);}if ( pid != 0 ){wait(NULL);printf( "Father Done\n" );}};void free_all( )// free all the pointers{int i;for( i = 0; i < 30; i++ )free(argv[i]);printf( "All the pointer have been free.." )};int main(){int flag;printf( "Please input a command,please using the '>'\n" );printf( "example: ls -ail > 123 \n" );flag = deal();if( flag == -1 ){fprintf( stderr, "input wrong! do not include '>'\n");exit(1);}execute( flag );free_all();return 0;}