//實用工具程序之一，作用是當新消息到達后向用戶終端顯示器上寫一個通知

#include <sys/types.h>#include <sys/stat.h>#include <utmp.h>#ifndef UTMP_FILE#ifdef _PATH_UTMP#define UTMP_FILE _PATH_UTMP#else#define UTMP_FILE "/etc/utmp"#endif#endif#include "readwrite.h"#include "stralloc.h"#include "substdio.h"#include "subfd.h"#include "open.h"#include "byte.h"#include "str.h"#include "headerbody.h"#include "hfield.h"#include "env.h"#include "exit.h"substdio ssutmp;char bufutmp[sizeof(struct utmp) * 16];int fdutmp;substdio sstty;char buftty[1024];int fdtty;struct utmp ut;char line[sizeof(ut.ut_line) + 1];stralloc woof = {0};stralloc tofrom = {0};stralloc text = {0};void doit(s,n) char *s; int n;{ if (!stralloc_catb(&text,s,n)) _exit(0); if (text.len > 78) text.len = 78;}void dobody(h) stralloc *h; { doit(h->s,h->len); }void doheader(h) stralloc *h;{ int i; if (hfield_known(h->s,h->len) == H_SUBJECT)  {   i = hfield_skipname(h->s,h->len);   doit(h->s + i,h->len - i);  }}void finishheader() { ; }void main(){ char *user; char *sender; char *userext; struct stat st; int i; if (chdir("/dev") == -1) _exit(0); if (!(user = env_get("USER"))) _exit(0); if (!(sender = env_get("SENDER"))) _exit(0); if (!(userext = env_get("LOCAL"))) _exit(0); if (str_len(user) > sizeof(ut.ut_name)) _exit(0); if (!stralloc_copys(&tofrom,"*** TO <")) _exit(0); if (!stralloc_cats(&tofrom,userext)) _exit(0); if (!stralloc_cats(&tofrom,"> FROM <")) _exit(0); if (!stralloc_cats(&tofrom,sender)) _exit(0); if (!stralloc_cats(&tofrom,">")) _exit(0); for (i = 0;i < tofrom.len;++i)   if ((tofrom.s[i] < 32) || (tofrom.s[i] > 126))     tofrom.s[i] = '_'; if (!stralloc_copys(&text,"    ")) _exit(0); if (headerbody(subfdin,doheader,finishheader,dobody) == -1) _exit(0); for (i = 0;i < text.len;++i)   if ((text.s[i] < 32) || (text.s[i] > 126))     text.s[i] = '/'; if (!stralloc_copys(&woof,"\015\n\007")) _exit(0); if (!stralloc_cat(&woof,&tofrom)) _exit(0); if (!stralloc_cats(&woof,"\015\n")) _exit(0); if (!stralloc_cat(&woof,&text)) _exit(0); if (!stralloc_cats(&woof,"\015\n")) _exit(0); fdutmp = open_read(UTMP_FILE); if (fdutmp == -1) _exit(0); substdio_fdbuf(&ssutmp,read,fdutmp,bufutmp,sizeof(bufutmp)); while (substdio_get(&ssutmp,&ut,sizeof(ut)) == sizeof(ut))   if (!str_diffn(ut.ut_name,user,sizeof(ut.ut_name)))    {     byte_copy(line,sizeof(ut.ut_line),ut.ut_line);     line[sizeof(ut.ut_line)] = 0;     if (line[0] == '/') continue;     if (!line[0]) continue;     if (line[str_chr(line,'.')]) continue;     fdtty = open_append(line);     if (fdtty == -1) continue;     if (fstat(fdtty,&st) == -1) { close(fdtty); continue; }     if (!(st.st_mode & 0100)) { close(fdtty); continue; }     if (st.st_uid != getuid()) { close(fdtty); continue; }     substdio_fdbuf(&sstty,write,fdtty,buftty,sizeof(buftty));     substdio_putflush(&sstty,woof.s,woof.len);     close(fdtty);    } _exit(0);}