File: quit.c

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/***************************************************************************
 *
 * $Header: /usr/local/cvsroot/utils/ytree/quit.c,v 1.13 2003/03/16 13:13:29 werner Exp $
 *
 * Verlassen von ytree
 *
 * 
 ***************************************************************************/


#include "ytree.h"

/*
quit-to-directory (xtree: alt-Q)(ytree: shift-Q, ^Q)
this uses the Ztree method.
for this to work, a ytree is called via a function in ~/.bashrc
instead of directly. that function generates a pid-unique
file containing a "cd cwd" line before calling ytree, and 
sources-in the pid-unique file afterward, thus jumping to the
directory specified.
if ytree rewrites that file to the quit-to dir, the eventual
command-prompt will be in that chosen dir.
thus, a Quit exit jumps to the dir it's already in. a QuitTo
exit jumps to the dir_entry-specified dir.

QuitTo:

- get parent's pid
- get owning uid's homedir
- compose shell stub name
- test: 
  - exists?
  - regular file?
  - non-zero length?
- write dir_entry to it, thus replacing the starting-cwd line
- chain to Quit

if user elects not to quit, no harm done: 

- rewrite that file to starting-cwd if it passes those checks again
  (avoiding race opening vuln)
- return to main program loop 

a user can have a bunch of ytrees open, but they'll be run one-per-
shell (i.e. each xterm singletasking) unless the user's ASKING for 
trouble, so a given shell-pid will be unique for the xterm that 
owns it, even though they're all clustered in the user's homedir.

changes:
- ytree.h		add	prototype for QuitTo
- filewin.c		add call to QuitTo, for Q and ^Q
- dirwin.c		add call to QuitTo, for Q and ^Q (q still falls to main)

i've mapped this to ^Q for now on my home machine, but it's probably best to
use just SHIFT-Q for this, following the trend of mapping XtreeGold
Alt-commands to SHIFT-commands in ytree/xtc. that leaves ytree usable in
serial terminals with soft (XOFF/XON) line control protocol.

in .bashrc:
#
# "yt" is part of getting ytree to quit to the target directory rather
# than the starting one (Alt-Q rather than Q, in XTG terms).
# the pid-numbered chdir "bat" will get rewritten to the selected
# dir if ytree is Quit or ^Quit rather than quit, if ytree-1.75b
# (or later version, assuming Werner incorporates my changes) is used. 
# This method is based on Kim Henkel's alt-Q batfile method for ZtreeWin.
#  --crb3 14jan00/12mar03
#
function yt
{
  echo cd $PWD >~/.ytree-$$.chdir
  /usr/bin/ytree $1 $2 $3 $4 $5
  source ~/.ytree-$$.chdir
  rm ~/.ytree-$$.chdir
}

*/

#define MAXPATH	(PATH_LENGTH+1)

static int QuitFileCheck(char *fname);




void QuitTo(DirEntry * dir_entry)
{
  int parpid;
  FILE *qfile;
  char nbuf[MAXPATH],qfilename[MAXPATH];
  struct passwd *pwp;
  
    GetPath(dir_entry,nbuf);
	parpid=getppid();
	pwp=getpwuid(getuid());
	sprintf(qfilename,"%s/.ytree-%d.chdir",pwp->pw_dir,parpid);

	if(!QuitFileCheck(qfilename)){
	  	if( (qfile=fopen(qfilename,"w"))!=NULL)
  		{
  			fprintf(qfile,"cd %s\n",nbuf);
			fclose(qfile);
		}
	}
	
	Quit();		/* never come back from a successful quit */

	if(!QuitFileCheck(qfilename)){
	  	if( (qfile=fopen(qfilename,"w"))!=NULL)
  		{
  			fprintf(qfile,"cd %s\n",Getcwd(NULL,0));
			fclose(qfile);
		}
	}
}

/*
 * QuitFileCheck.
 * quick safety-check of the shell stub we want to write to.
 * if any of these tests fail, somebody's trying to use us for a 
 * security breach. 
 */

static int QuitFileCheck(char *fname)
{
  struct stat fstat;

	if(stat(fname,&fstat))
		return(1);
	if(!S_ISREG(fstat.st_mode))
		return(1);
	if(!fstat.st_size)
		return(2);
	if(fstat.st_uid != getuid())
		return(3);
	return(0);
}


void Quit(void)
{
  int term;
  char path[PATH_LENGTH + 1];
  char *p;

  term = InputChoise( "quit ytree (Y/N) ?", "YNQq\r\033" );

  if( term == 'Y' || term == 'Q' || term == 'q' )
  {
    if (( p = getenv("HOME") ))
    {
      sprintf(path, "%s%c%s", p, FILE_SEPARATOR_CHAR, HISTORY_FILENAME);
      SaveHistory(path);
    }
    endwin();
#ifdef XCURSES
    XCursesExit();
#endif
    exit( 0 );
  }
}