filestat.c File Reference

Utility functions for handling file links and retrieving file information. More...

#include <unistd.h>
#include "mdb.h"

Go to the source code of this file.

Functions
char *	dir_name (const char *path)
	Retrieves the leading directories from a given path.
char *	read_file_link (const char *filename)
	Reads the first link of a file.
const char *	read_file_lastlink (const char *filename)
	Retrieves the last link in a chain of symbolic links.
char *	read_last_link_to_file (const char *filename)
	Resolves the final target file that a symbolic link points to.
long	get_file_stat (const char *filename, const char *final_file, struct stat *filestat)
	Retrieves the file status of a given file or its final link target.
long	file_is_modified (const char *inputfile, char **final_file, struct stat *input_stat)
	Checks if a file has been modified.

Detailed Description

Utility functions for handling file links and retrieving file information.

Copyright

• (c) 2002 The University of Chicago, as Operator of Argonne National Laboratory.
• (c) 2002 The Regents of the University of California, as Operator of Los Alamos National Laboratory.

License

This file is distributed under the terms of the Software License Agreement found in the file LICENSE included with this distribution.

Author

H. Shang, M. Borland, R. Soliday

Definition in file filestat.c.

Function Documentation

dir_name()

char * dir_name

(

const char *

path

)

Retrieves the leading directories from a given path.

Allocates memory for the leading directories part of the provided PATH. If memory allocation fails, returns NULL. Assumes that any trailing slashes in PATH have already been removed. This function avoids using the dirname builtin to maintain consistent behavior across different environments.

Parameters

path	The file path from which to extract the leading directories.

Returns

A newly allocated string containing the leading directories, or NULL if out of memory.

Definition at line 33 of file filestat.c.

                                 {
  char *newpath = NULL;
  const char *slash = NULL;
  int length; /* Length of result, not including NUL.  */
 
  slash = strrchr(path, '/');
  if (slash == 0) {
    /* File is in the current directory.  */
    path = ".";
    length = 1;
  } else {
    /* Remove any trailing slashes from the result.  */
    while (slash > path && *slash == '/')
      --slash;
    length = slash - path + 1;
  }
  newpath = (char *)malloc(length + 1);
  if (newpath == 0)
    return 0;
  strncpy(newpath, path, length);
  newpath[length] = 0;
  return newpath;
}

file_is_modified()

long file_is_modified	(	const char *	inputfile,
		char **	final_file,
		struct stat *	input_stat )

Checks if a file has been modified.

Determines whether the specified input file has been modified by comparing its current state against a previously recorded state. If the file is a symbolic link, it checks the final target file for modifications. The function updates the final_file pointer if the link target has changed.

Parameters

inputfile	The path to the input file to check for modifications.
final_file	Pointer to a string containing the final target file name. May be updated.
input_stat	Pointer to a struct stat containing the previous state of the file.

Returns

1 if the file has been modified or the link target has changed, 0 otherwise.

Definition at line 191 of file filestat.c.

                                                                                         {
  struct stat filestat;
  char *tempfile = NULL;
  const char *tmpinput = NULL;
 
  if (!fexists(inputfile)) {
    fprintf(stderr, "%s file does not exist!\n", inputfile);
    return (1);
  }
  if (*final_file && !fexists(*final_file)) {
    fprintf(stderr, "linked file %s of inputfile %s does not exist!\n", *final_file, inputfile);
    return (1);
  }
  if (!input_stat) {
    fprintf(stderr, "The previous state of file %s is not known.\n", inputfile);
    return (1);
  }
 
  tempfile = read_last_link_to_file(inputfile);
 
  /*the final link name changed */
  if (tempfile && *final_file && strcmp(tempfile, *final_file)) {
    if (*final_file)
      free(*final_file);
    *final_file = tempfile;
    return 1;
  }
  if ((tempfile && !(*final_file)) || (!tempfile && *final_file)) {
    if (*final_file)
      free(*final_file);
    *final_file = tempfile;
    return 1;
  }
  /* the final link name did not change, check if the file state changed */
  if (tempfile)
    free(tempfile);
  if (*final_file)
    tmpinput = *final_file;
  else
    tmpinput = inputfile;
  filestat = *input_stat;
  if (stat(tmpinput, input_stat) != 0) {
    fprintf(stderr, "Problem getting modification time for %s\n", tmpinput);
    exit(1);
  }
  if (input_stat->st_ctime != filestat.st_ctime) {
    /* file state is changed */
    return 1;
  }
  return 0;
}

get_file_stat()

long get_file_stat	(	const char *	filename,
		const char *	final_file,
		struct stat *	filestat )

Retrieves the file status of a given file or its final link target.

Obtains the file status information for the specified filename. If the file is a symbolic link and a final_file is provided, it retrieves the status of the final target file. If the file does not exist or an error occurs during the retrieval, an error message is printed to stderr.

Parameters

filename	The name of the file to retrieve the status for.
final_file	Optional parameter specifying the final target file if filename is a link.
filestat	Pointer to a struct stat where the file status will be stored.

Returns

0 on success, 1 on failure.

Definition at line 162 of file filestat.c.

                                                                                        {
  const char *input = NULL;
  if (!fexists(filename)) {
    fprintf(stderr, "%s file does not exist, unable to get the state of it!\n", filename);
    return (1);
  }
  input = filename;
  if (final_file)
    input = final_file;
  if (stat(input, filestat) != 0) {
    fprintf(stderr, "Problem getting state of file %s\n", input);
    return (1);
  }
  return 0;
}

read_file_lastlink()

const char * read_file_lastlink

(

const char *

filename

)

Retrieves the last link in a chain of symbolic links.

Traverses the chain of symbolic links starting from the given filename and returns the name of the last link that directly points to the final target file. If the file is not a link, returns the original filename.

Parameters

filename

The starting file name to resolve the last link from.

Returns

The name of the last link in the chain, or the original filename if not a link.

Definition at line 112 of file filestat.c.

                                                     {
  char *linkname = NULL;
  const char *lastlink = NULL;
  lastlink = filename;
  while ((linkname = read_file_link(filename)) != NULL) {
    lastlink = filename;
    filename = linkname;
  }
  return lastlink;
}

read_file_link()

char * read_file_link

(

const char *

filename

)

Reads the first link of a file.

Returns the first link of the specified file. If the file is not a link or if an error occurs (including unsupported platforms), returns NULL. On successful retrieval, the returned string is dynamically allocated and should be freed by the caller.

Parameters

filename

The name of the file to read the link from.

Returns

A newly allocated string containing the link target, or NULL if not a link or on error.

Definition at line 68 of file filestat.c.

                                           {
#if defined(_WIN32) || defined(vxWorks)
  return (NULL);
#else
  int size = 100, nchars = -1;
  char *tmpbuf = NULL, *dir = NULL, *tempname = NULL;
  tmpbuf = (char *)calloc(size, sizeof(char));
  while (1) {
    nchars = readlink(filename, tmpbuf, size);
    if (nchars < 0) {
      free(tmpbuf);
      return NULL;
    }
    if (nchars < size) {
      if (tmpbuf[0] == '/')
        return tmpbuf;
      else {
        dir = dir_name(filename);
        tempname = (char *)malloc(sizeof(char) * (strlen(filename) + strlen(tmpbuf) + 2));
        tempname[0] = 0;
        strcat(tempname, dir);
        strcat(tempname, "/");
        strcat(tempname, tmpbuf);
        free(tmpbuf);
        free(dir);
        return tempname;
      }
    }
    size *= 2;
    tmpbuf = (char *)realloc(tmpbuf, sizeof(char) * size);
  }
#endif
}

read_last_link_to_file()

char * read_last_link_to_file

(

const char *

filename

)

Resolves the final target file that a symbolic link points to.

Follows the chain of symbolic links starting from the given filename and returns the name of the final target file. The returned string is dynamically allocated and should be freed by the caller. If the filename is not a link, returns NULL.

Parameters

filename

The starting file name to resolve to the final target.

Returns

A newly allocated string containing the final target file name, or NULL if not a link.

Definition at line 134 of file filestat.c.

                                                   {
  char *linkname = NULL;
  char *tmpname = NULL;
 
  if ((linkname = read_file_link(filename)) == NULL)
    return NULL;
  tmpname = (char *)calloc(1024, sizeof(char));
  do {
    strcpy_ss(tmpname, linkname);
    free(linkname);
    linkname = read_file_link(tmpname);
  } while (linkname != NULL);
  return tmpname;
}