proc_getcwd, get the working dir of arbitrary process (BSD/macOS)

cwdtool.c

/*
 * Copyright 2008 Sam Thorogood. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
 
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <libproc.h>
#include <string.h>

/**
 * proc_getcwd -- get the working directory of an arbitrary process (BSD)
 *
 * This function copies the absolute pathname of the current working directory
 * into the pointer `ptr`, allocating if it is not passed. This buffer (if
 * pre-allocated) should be MAXPATHLEN bytes long.
 *
 * Note that this will fail if a program does not have enough rights to access
 * this information. Typically this means the target must have the same
 * effective UID, or the program calling this function must be root.
 *
 */
char *proc_getcwd( int pid, char *ptr ) {

	struct proc_vnodepathinfo vpi;

	/* grab proc info via bsd call */
	if( 0 >= proc_pidinfo( pid, PROC_PIDVNODEPATHINFO, 0, &vpi, sizeof( vpi ) ) ) {
		return NULL;
	}

	/* allocate space if required */
	if( !ptr ) {
		if( !( ptr = ( char * ) malloc( MAXPATHLEN ) ) ) {
			errno = ENOMEM;
			return NULL;
		}
	}

	/* copy data into output buffer, return */
	strcpy( ptr, vpi.pvi_cdir.vip_path );
	return ptr;

}

int main( int argc, char **argv ) {

	int i, pid;
	char *buf;

	for( i = 1; i < argc; ++i ) {
		pid = atoi( argv[i] );
		printf( "%d:\n", pid );

		buf = proc_getcwd( pid, NULL );
		if( !buf ) {
			fprintf( stderr, "can't get cwd of proc %d (%s)\n", pid, strerror( errno ) );
			exit( 1 );
		}
		printf( "%s\n", buf );
		free( buf );

	}

}