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how to check the actual path instead of link path


 
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# 1  
Old 10-01-2006
how to check the actual path instead of link path

Hi

I have a path link
/test/df/link1/actual/file1

here link1 is actually a softlink link1= a/b

i need to print the ACTUAL FULL path instead of a linked path

is there any direct command to print the actual path of any linked path
eg
showPhyscialPath /test/df/link1/actual/file1 and it prints the full path

i know that i can do using
cd /test/df/link1/actual/file1/
and then pwd -P
shows the actual full path, i dont want to change the directory and then used pwd

Thaknks
Rel
# 2  
Old 10-02-2006
You can use 'ls' with the -L option.
Code:
       -L, --dereference
              when showing file information for a symbolic link, show information for  the
              file the link references rather than for the link itself

# 3  
Old 10-02-2006
thanks for reply
but ls -L just works for link and does not work for any directory after link or before link

if i do
ls -L link1 then it will show the actual right side value of link1

but if we do
ls -L link1/newdir then it wont show anything

in my case i dont even which one is link, but i want to know the actual path if there is any link anywhere in the path
# 4  
Old 10-04-2006
well, maybe it going to be little hard to understand, but I hope it helps in another case.

When I want to catch somebody's real path of a process execution (I already know the process ID) I used to use "pwdx PID" this is a Solaris utility (you can check it doing a: man proc)

"proc" is a set of tools some times weird, some times very helpful.

Hope it works
# 5  
Old 10-04-2006
There's a reason for this. To find out what a link "really is" requires making a system call, readlink. In most circumstances, open (the system call used to open a file) is the only call that does this automatically. I don't know of a command line utility this does the readlink. A long time ago, we needed something to do this - here is a small utility to do that. This could be written in other languages, it happens to be C.
Code:
#include <sys/types.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <limits.h>
#include <string.h>
#include <stddef.h>
#include <pwd.h>

#define ck_null(x) if((x)==NULL){perror(""); exit(EXIT_FAILURE);}
#define ck_ltz(x) if((x)==(-1)){perror(""); exit(EXIT_FAILURE);}
#ifndef PATH_MAX
#define PATH_MAX 255
#endif
#define DEPTH 16

size_t signal_arglen =0;
char signal_buffer[PATH_MAX+1]={0x0};

void sig_int(int signo)
{
	write(STDERR_FILENO,signal_buffer,signal_arglen);
	exit(EXIT_FAILURE);
}

void expand_path(char *path)
{
	char *prepend=malloc(2*PATH_MAX);
    char *ptr=path;    
	ck_null(prepend);

	if(memcmp(path,"~/",2)==0 || memcmp(path,"./",2)==0)
	{
		struct passwd *pw=NULL;
	    char tmp[PATH_MAX+1]={0x0};	    
	    
		ptr++;       
		switch(*path)
		{
			case '.':				
				sprintf(prepend,"%s%s", getcwd(tmp,PATH_MAX), ptr);
				break;
			case '~':  /* not normally executed ~/ expanded by shell */
				pw=getpwuid(getuid() );
				sprintf(prepend,"%s%s", pw->pw_dir, ptr);
				break;
			default:
				break;			
		}
		strcpy(path,prepend);
    }
    free(prepend);	
}


void get_link_info(char *path)
{
	char buf[PATH_MAX+1]={0x0};
	ssize_t buflen=readlink(path,buf,PATH_MAX);
	
	if(buflen>0)
	{
	    char *p=strrchr(path,'/');	
	    if(p==NULL) 
	        p=path;	   	   
	    buf[buflen]=0x0;
	    strcpy(p,buf);
    }	
}

void recurse_path(char elements[][PATH_MAX],char *path)
{
	int i=0;
    char *p=path;
    char *q=NULL;
        
    if(*p=='/') i=(-1); 
    if(strchr(path,'/')==NULL)
    {
    	strcpy(elements[0],path);	
    }
    else
    {  
		for(p=path;*p;p++)
		{
			if(*p=='/')			
				q=elements[++i];				
    	    *q++=*p;
		}	
     }
}

char  *get_path_elements(char *dest, char *path)
{
	char *working=calloc(1,PATH_MAX*2);
	int i=0;
	char elements[DEPTH][PATH_MAX]={0x0};
	
	ck_null(working);	
	recurse_path(elements,path);
	while(*elements[i])	
	{
		strcat(working,elements[i++]);
		get_link_info(working);	
	}
	strcpy(dest,working);
	free(working);
	return dest;
}

int main(int argc, char *argv[])
{
	char path[PATH_MAX*2]={0x0};
	char working_path[PATH_MAX*2]={0x0};
	int i=1;
    char *p=argv[i];

	sprintf(signal_buffer,"%s interrupt\n",argv[0]);
    signal_arglen=strlen(signal_buffer);	
	signal(SIGINT,sig_int);
	if (argc >1)
	{
	    while(*p)
	    {
	    	strcpy(working_path,p);
	    	expand_path(working_path);
	    	printf("%s\n",
	    	        get_path_elements(path, working_path));
	    	i++;
	    	p=argv[i];
	    }
	}
	else
	{
		while(fgets(working_path,sizeof(working_path),stdin)!=NULL)
		{
			expand_path(working_path);
	    	printf("%s\n",
	    	        get_path_elements(path, working_path));		
		}
	}
	return 0;
}


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