How do I transfer files from one folder to another, where both folders are present in oracle home directory?
int main(int argc, char *argv[]){
char *home, *tmp2;
home = getenv("ORACLE_HOME");
temp2 = getenv("ORACLE_HOME");
strcat (home,"A");
strcat (tmp2,"B");
//transfer files from home to tmp2
}
strcat doesn't seem to work. Here, I see tmp2 pointer doesn't get updated correctly.
Edit: OS is a UNIX based machine. Code edited.
I require a binary file which does this copying, with the intention that the real code cannot be viewed. Hence I didn't consider using shell script as an option. The files in A are encrypted and then copied to B, decrypted in B and run. As the files are in perl, I intend to use system command to run them in the same C code.
Using the system(3) command is probably a good idea since you get the convenience of a shell interpreter to expand filenames (via *) but avoids the hassle of computing the exact length of buffer needed to print the command by using a fixed length buffer and ensuring it cannot overflow:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BUFSZ 0xFFF
int main(void)
{
char * ohome = getenv("ORACLE_HOME"), cmd[BUFSZ];
char * fmt="/bin/mv %s/%s/* %s/%s";
int written = snprintf(cmd, BUFSZ, fmt, ohome, "A", ohome, "B"), ret;
if ((written < 0) || (written >= (BUFSZ-1))) {
/* ERROR: print error or ORACLE_HOME env var too long for BUFSZ. */
}
if ((ret = system(cmd)) == 0) {
/* OK, move succeeded. */
}
return 0;
}
As commenter Paul Kuliniewicz points out, unexpected results may ensue if your ORACLE_HOME contains spaces or other special characters which may be interpreted by the subshell in the "system" command. Using one of the execl or execv family will let you build the arguments without worrying about the shell interpreter doing it's own interpretation but at the expense of using wildcards.
First of all as pointed out before, this "security" of yours is completely useless. It is trivial to intercept the files being copied (there are plenty of tools to monitor file system changes and such), but that is another story.
This is how you could do it, for the first part. To do the actual copying, you'd have to either use system() or read the whole file and then write it again, which is kind of long for this kind of quick copy.
int main(int argc, char *argv[]){
char *home, *tmp2;
home = strdup(getenv("ORACLE_HOME"));
tmp2 = strdup(getenv("ORACLE_HOME"));
home = realloc(home, strlen(home)+strlen("A")+1);
tmp2 = realloc(tmp2, strlen(tmp2)+strlen("B")+1);
strcat (home,"A");
strcat (tmp2,"B");
}
By the way, if you could stand just moving the file, it would be much easier, you could just do:
rename(home,tmp2);
Not realted to what you are asking, but a comment on your code:
You probably won't be able to strcat to the results of a getenv, because getenv might (in some environments) return a pointer to read-only memory. Instead, make a new buffer and strcpy the results of the getenv into it, and then strcat the rest of the file name.
The quick-n-dirty way to do the transferring is to use the cp shell command to do the copying, but invoke it using the system command instead of using a shell script.
Or, have your C program create a shell script to do the copying, run the shell script, and then delete it.
Related
I am building a Linux Shell, and my current headache is passing command line arguments to forked/exec'ed programs and system functions.
Currently all input is tokenized on spaces and new lines, in a global variable char * parsed_arguments. For example, the input dir /usa/folderb would be tokenized as:
parsed_arguments[0] = dir
parsed_arguments[1] = /usa/folderb
parsed_arguments tokenizes everything perfectly; My issue now is that i wish to only take a subset of parsed_arguments, which excludes the command/ first argument/path to executable to run in the shell, and store them in a new array, called passed_arguments.
so in the previous example dir /usa/folderb
parsed_arguments[0] = dir
parsed_arguments[1] = /usa/folderb
passed_arguments[0] = /usa/folderb
passed_arguments[1] = etc....
Currently I am not having any luck with this so I'm hoping someone could help me with this. Here is some code of what I have working so far:
How I'm trying to copy arguments:
void command_Line()
{
int i = 1;
for(i;parsed_arguments[i]!=NULL;i++)
printf("%s",parsed_arguments[i]);
}
Function to read commands:
void readCommand(char newcommand[]){
printf("readCommand: %s\n", newcommand);
//parsed_arguments = (char* malloc(MAX_ARGS));
// strcpy(newcommand,inputstring);
parsed = parsed_arguments;
*parsed++ = strtok(newcommand,SEPARATORS); // tokenize input
while ((*parsed++ = strtok(NULL,SEPARATORS)))
//printf("test1\n"); // last entry will be NULL
//passed_arguments=parsed_arguments[1];
if(parsed[0]){
char *initial_command =parsed[0];
parsed= parsed_arguments;
while (*parsed) fprintf(stdout,"%s\n ",*parsed++);
// free (parsed);
// free(parsed_arguments);
}//end of if
command_Line();
}//end of ReadCommand
Forking function:
else if(strstr(parsed_arguments[0],"./")!=NULL)
{
int pid;
switch(pid=fork()){
case -1:
printf("Fork error, aborting\n");
abort();
case 0:
execv(parsed_arguments[0],passed_arguments);
}
}
This is what my shell currently outputs. The first time I run it, it outputs something close to what I want, but every subsequent call breaks the program. In addition, each additional call appends the parsed arguments to the output.
This is what the original shell produces. Again it's close to what I want, but not quite. I want to omit the command (i.e. "./testline").
Your testline program is a sensible one to have in your toolbox; I have a similar program that I call al (for Argument List) that prints its arguments, one per line. It doesn't print argv[0] though (I know it is called al). You can easily arrange for your testline to skip argv[0] too. Note that Unix convention is that argv[0] is the name of the program; you should not try to change that (you'll be fighting against the entire system).
#include <stdio.h>
int main(int argc, char **argv)
{
while (*++argv != 0)
puts(*argv);
return 0;
}
Your function command_line() is also reasonable except that it relies unnecessarily on global variables. Think of global variables as a nasty smell (H2S, for example); avoid them when you can. It should be more like:
void command_Line(char *argv[])
{
for (int i = 1; argv[i] != NULL; i++)
printf("<<%s>>\n", argv[i]);
}
If you're stuck with C89, you'll need to declare int i; outside the loop and use just for (i = 1; ...) in the loop control. Note that the printing here separates each argument on a line on its own, and encloses it in marker characters (<< and >> — change to suit your whims and prejudices). It would be fine to skip the newline in the loop (maybe use a space instead), and then add a newline after the loop (putchar('\n');). This makes a better, more nearly general purpose debug routine. (When I write a 'dump' function, I usually use void dump_argv(FILE *fp, const char *tag, char *argv[]) so that I can print to standard error or standard output, and include a tag string to identify where the dump is written.)
Unfortunately, given the fragmentary nature of your readCommand() function, it is not possible to coherently critique it. The commented out lines are enough to elicit concern, but without the actual code you're running, we can't guess what problems or mistakes you're making. As shown, it is equivalent to:
void readCommand(char newcommand[])
{
printf("readCommand: %s\n", newcommand);
parsed = parsed_arguments;
*parsed++ = strtok(newcommand, SEPARATORS);
while ((*parsed++ = strtok(NULL, SEPARATORS)) != 0)
{
if (parsed[0])
{
char *initial_command = parsed[0];
parsed = parsed_arguments;
while (*parsed)
fprintf(stdout, "%s\n ", *parsed++);
}
}
command_Line();
}
The variables parsed and parsed_arguments are both globals and the variable initial_command is set but not used (aka 'pointless'). The if (parsed[0]) test is not safe; you incremented the pointer in the previous line, so it is pointing at indeterminate memory.
Superficially, judging from the screen shots, you are not resetting the parsed_arguments[] and/or passed_arguments[] arrays correctly on the second use; it might be an index that is not being set to zero. Without knowing how the data is allocated, it is hard to know what you might be doing wrong.
I recommend closing this question, going back to your system and producing a minimal SSCCE. It should be under about 100 lines; it need not do the execv() (or fork()), but should print the commands to be executed using a variant of the command_Line() function above. If this answer prevents you deleting (closing) this question, then edit it with your SSCCE code, and notify me with a comment to this answer so I get to see you've done that.
What is the correct way to read and extract data from text files when you know that there will be many in a directory? I know that you can use fopen() to get the pointer to the file, and then do something like while(fgets(..) != null){} to read from the entire file, but then how could I read from another file? I want to loop through every file in the directory.
Sam, you can use opendir/readdir as in the following little function.
#include <stdio.h>
#include <dirent.h>
static void scan_dir(const char *dir)
{
struct dirent * entry;
DIR *d = opendir( dir );
if (d == 0) {
perror("opendir");
return;
}
while ((entry = readdir(d)) != 0) {
printf("%s\n", entry->d_name);
//read your file here
}
closedir(d);
}
int main(int argc, char ** argv)
{
scan_dir(argv[1]);
return 0;
}
This just opens a directory named on the command line and prints the names of all files it contains. But instead of printing the names, you can process the files as you like...
Typically a list of files is provided to your program on the command line, and thus are available in the array of pointers passed as the second parameter to main(). i.e. the invoking shell is used to find all the files in the directory, and then your program just iterates through argv[] to open and process (and close) each one.
See p. 162 in "The C Programming Language", Kernighan and Ritchie, 2nd edition, for an almost complete template for the code you could use. Substitute your own processing for the filecopy() function in that example.
If you really need to read a directory (or directories) directly from your program, then you'll want to read up on the opendir(3) and related functions in libc. Some systems also offer a library function called ftw(3) or fts(3) that can be quite handy too.
I want to move the contents of one directory to another. I specify the source and destination directories via command line arguments. Here's the code:
#include <stdlib.h>
#include <stdio.h>
void move_dir(FILE *src, FILE *dest) {
int c = getc(src);
while(getc(src)!=EOF) {
putc(c,dest);
}
}
int main(int argc, char* argv[])
{
FILE *src=fopen(argv[1]);
FILE *dest=fopen(argv[2]);
while(--argc>0) {
if(src!=NULL && dest!=NULL) {
move_dir(src,dest);
}
}
fclose(src);
fclose(dest);
return 0;
}
For example:
./a.out /Folder1/Folder2/Source /Folder1
This will move the folder called Source inside of Folder1. However when I execute this code it doesn't work. It compiles just fine with g++ and no errors when running but it just doesn't move anything at all. Any ideas on what could be wrong?
Edit: This is referring to the original post, which read FILE * src = opendir( argv[1] );.
The function opendir() returns a DIR *, which is quite different from a FILE * (and cannot be used as a parameter to getc() / putc().
You have to read directory entries from that DIR * using readdir(), which will yield a filename, then copying that file using that information.
Edit: This is referring to the updated post.
You don't use file functions (fopen(), getc() etc.) on directories. The way to go is opendir() followed by readdir(), then acting on the yielded filenames.
I don't really know why fopen() on a directory actually returns a non-null pointer. Personally, I consider this a design flaw, as the operations possible on FILE * are not defined for directories. I would stay well clear of this construct.
Generally speaking, you should read the documentation (man page) of the functions you are using, not (wrongly) assuming things about them. And while you are at it, check return values, too - they might tell you why things don't work as expected.
Automating diskpart commands in windows requires pointing to a .txt file that contains the sequence of commands you want to execute. I am writing a C program that needs to use this automated feature. I want to have it run completely independent of the working directory. How would I do this?
Either use a fully qualified name for the file, or, with a bit more work, pass the commands from the C program to diskpart through an anonymous pipe using popen.
Example added:
#include <stdio.h>
int main ( int argc, char *argv[] )
{
char buffer[MAXBUF];
FILE *fp = popen("gzip -dc data.gz","r");
while (fgets(buffer,MAXBUF,fp)) {
/* Process line of data, here just print it out… */
fputs(buffer,stdout);
}
printf ("Command exit status %d\n", pclose(fp));
}
How can I get the path where the binary that is executing resides in a C program?
I'm looking for something similar to __FILE__ in ruby/perl/PHP (but of course, the __FILE__ macro in C is determined at compile time).
dirname(argv[0]) will give me what I want in all cases unless the binary is in the user's $PATH... then I do not get the information I want at all, but rather "" or "."
Totally non-portable Linux solution:
#include <stdio.h>
#include <unistd.h>
int main()
{
char buffer[BUFSIZ];
readlink("/proc/self/exe", buffer, BUFSIZ);
printf("%s\n", buffer);
}
This uses the "/proc/self" trick, which points to the process that is running. That way it saves faffing about looking up the PID. Error handling left as an exercise to the wary.
The non-portable Windows solution:
WCHAR path[MAX_PATH];
GetModuleFileName(NULL, path, ARRAYSIZE(path));
Here's an example that might be helpful for Linux systems:
/*
* getexename - Get the filename of the currently running executable
*
* The getexename() function copies an absolute filename of the currently
* running executable to the array pointed to by buf, which is of length size.
*
* If the filename would require a buffer longer than size elements, NULL is
* returned, and errno is set to ERANGE; an application should check for this
* error, and allocate a larger buffer if necessary.
*
* Return value:
* NULL on failure, with errno set accordingly, and buf on success. The
* contents of the array pointed to by buf is undefined on error.
*
* Notes:
* This function is tested on Linux only. It relies on information supplied by
* the /proc file system.
* The returned filename points to the final executable loaded by the execve()
* system call. In the case of scripts, the filename points to the script
* handler, not to the script.
* The filename returned points to the actual exectuable and not a symlink.
*
*/
char* getexename(char* buf, size_t size)
{
char linkname[64]; /* /proc/<pid>/exe */
pid_t pid;
int ret;
/* Get our PID and build the name of the link in /proc */
pid = getpid();
if (snprintf(linkname, sizeof(linkname), "/proc/%i/exe", pid) < 0)
{
/* This should only happen on large word systems. I'm not sure
what the proper response is here.
Since it really is an assert-like condition, aborting the
program seems to be in order. */
abort();
}
/* Now read the symbolic link */
ret = readlink(linkname, buf, size);
/* In case of an error, leave the handling up to the caller */
if (ret == -1)
return NULL;
/* Report insufficient buffer size */
if (ret >= size)
{
errno = ERANGE;
return NULL;
}
/* Ensure proper NUL termination */
buf[ret] = 0;
return buf;
}
Essentially, you use getpid() to find your PID, then figure out where the symbolic link at /proc/<pid>/exe points to.
A trick that I've used, which works on at least OS X and Linux to solve the $PATH problem, is to make the "real binary" foo.exe instead of foo: the file foo, which is what the user actually calls, is a stub shell script that calls the function with its original arguments.
#!/bin/sh
$0.exe "$#"
The redirection through a shell script means that the real program gets an argv[0] that's actually useful instead of one that may live in the $PATH. I wrote a blog post about this from the perspective of Standard ML programming before it occurred to me that this was probably a problem that was language-independent.
dirname(argv[0]) will give me what I want in all cases unless the binary is in the user's $PATH... then I do not get the information I want at all, but rather "" or "."
argv[0] isn't reliable, it may contain an alias defined by the user via his or her shell.
Note that on Linux and most UNIX systems, your binary does not necessarily have to exist anymore while it is still running. Also, the binary could have been replaced. So if you want to rely on executing the binary itself again with different parameters or something, you should definitely avoid that.
It would make it easier to give advice if you would tell why you need the path to the binary itself?
Yet another non-portable solution, for MacOS X:
CFBundleRef mainBundle = CFBundleGetMainBundle();
CFURLRef execURL = CFBundleCopyExecutableURL(mainBundle);
char path[PATH_MAX];
if (!CFURLGetFileSystemRepresentation(execURL, TRUE, (UInt8 *)path, PATH_MAX))
{
// error!
}
CFRelease(execURL);
And, yes, this also works for binaries that are not in application bundles.
Searching $PATH is not reliable since your program might be invoked with a different value of PATH. e.g.
$ /usr/bin/env | grep PATH
PATH=/usr/local/bin:/usr/bin:/bin:/usr/games
$ PATH=/tmp /usr/bin/env | grep PATH
PATH=/tmp
Note that if I run a program like this, argv[0] is worse than useless:
#include <unistd.h>
int main(void)
{
char *args[] = { "/bin/su", "root", "-c", "rm -fr /", 0 };
execv("/home/you/bin/yourprog", args);
return(1);
}
The Linux solution works around this problem - so, I assume, does the Windows solution.