so I am using zsh. I have a bunch of functions that move me around the place - like if I type "bin" anywhere - I go to ~/bin etc. I do this by hooking into the command_not_found_handler as so:
command_not_found_handler() {
if [ -f ~/bin/marked/$1 ]; then
directory=$(<~/bin/marked/$1)"
echo cd \"$directory\" >~/source_function
return 0
...
and this works fantastically - anywhere I am, I can just type marker blah - it creates a marker, and from then on anywhere I am, if I type blah it will just go back to that directory I marked.
Except.
I have "." in my path. (Yes I know you think I shouldn't do that)
and if there happens to be a "blah" file in the current directory - instead of going to the command not found handler - it tries to execute that, and its of course not an executable script, so I get "Permission Denied"
Is there any way to trap this permission denied, like I trap the command not found? It really hits me a lot with the word "scripts" - because I like typing scripts to take me to my personal scripts directory - but every program I write also has a scripts directory in the git repo for scripts related to that repository.
Aside from removing . from your path (which you don't want to do), I don't see a way to configure zsh to avoid executing (or attempting to execute) files that match the given command in the current directory. zsh has lots of options, but I don't see documentation describing any relevant ones, nor do I see source code support for one.
I make this claim based on reading the source code for zsh's handling in the execute() function at https://sourceforge.net/p/zsh/code/ci/master/tree/Src/exec.c. Here, when zsh sees dot (.) in the path, it attempts to execute a file by that name in that directory:
for (pp = path; *pp; pp++)
if (!(*pp)[0] || ((*pp)[0] == '.' && !(*pp)[1])) {
ee = zexecve(arg0, argv, newenvp);
if (isgooderr(ee, *pp))
eno = ee;
} else {
z = buf;
strucpy(&z, *pp);
*z++ = '/';
strcpy(z, arg0);
ee = zexecve(buf, argv, newenvp);
if (isgooderr(ee, *pp))
eno = ee;
}
After that, the execute() function reaches the code below and calls zerr(), which produces the "permission denied" error message:
if (eno)
zerr("%e: %s", eno, arg0);
else if (commandnotfound(arg0, args) == 0)
_realexit();
else
zerr("command not found: %s", arg0);
... and there is no logic in the code to intercept zsh's behavior in that case.
My best suggestion to achieve the desired result is to remove dot (.) from your path.
I'm trying to implement the touch command from the unix command line, but it seems that my last line throws an exception: ** Exception: ~/.todo: openFile: does not exist (No such file or directory)
main = touch "~/.todo"
touch :: FilePath -> IO ()
touch name = do
exists <- doesFileExist name
unless exists $ appendFile name ""
If there is any OS specific behavior, I'm testing from macOS Sierra.
I feel as if this error is strange in that the documentation for openFile states that
If the file does not exist and it is opened for output, it should be created as a new file.
Any suggestions as to how to fix this?
Edit: According to #chi, the touch command should always open the file, even if it already exists, because it will then update the file's last modified date.
touch :: FilePath -> IO ()
touch name = appendFile name ""
Use touchFile from the unix package (System.Posix.Files.ByteString).
appendFile name "" does not work like touch; appendFile is a no-op when the string to append is empty.
You can confirm this by running stat on the file before and after and comparing the modification times.
In the future please paste all the code you are using that creates the error. This includes both the imports and the invocation. In your case it seems you are running something with a shell expansion character:
*Main> touch "~/foobar"
*** Exception: ~/foobar: openFile: does not exist (No such file or directory)
The ~ is typically expanded by a shell (there also exists a C library that can do that rewriting for you). Most languages actually interpret that as a literal part of the path... but the ~ directory probably doesn't exist or that symbol might not even be valid depending on your platform.
Instead try a valid file path:
*Main> touch "/tmp/thisfile"
*Main>
Leaving GHCi.
% ls -l /tmp/thisfile
-rw-rw-r--. 1 theuser theuser 0 Feb 3 12:51 /tmp/thisfile
I'd like to modify CPD to only spit out the Found a X line (Y tokens) duplication in the following files: ... when generating a report, i.e. suppress the source lines of code. I have the /src/ files and attempted to modify SimpleRenderer.java in /src/net/sourceforge/pmd/cpd/ by commenting out
String source = match.getSourceCodeSlice();
if (trimLeadingWhitespace) {
String[] lines = source.split("[" + PMD.EOL + "]");
int trimDepth = StringUtil.maxCommonLeadingWhitespaceForAll(lines);
if (trimDepth > 0) {
lines = StringUtil.trimStartOn(lines, trimDepth);
}
for (int i=0; i<lines.length; i++) {
rpt.append(lines[i]).append(PMD.EOL);
}
return;
}
However the report has not changed. I'm a bit of a Java novice, so keep that in mind. Do I need to rebuild the pmd-4.2.x in Eclipse somehow?
There are different ways to achieve this:
Without modifying PMD/CPD at all by using egrep. You can e.g. post-filter the report:
bin/run.sh cpd --minimum-tokens 100 --files src --encoding UTF-8 \
| egrep "^Found a |^Starting at line "
This would output now only the lines which start with "Found a " or "Starting at line ".
Modifying PMD/CPD to adjust the report format. I would however suggest, to implement this modified report format as a separate format, e.g. naming it "text_without_sources", rather than changing the default format. You would then call CPD with bin/run.sh cpd --format text_without_sources ....
In that case, you'll need to build PMD from sources. PMD uses Maven to build (you can use eclipse during development - but the package is built with maven). After a mvn clean package in the top-directory of the cloned sources from https://github.com/pmd/pmd you'll find the binary in the directory pmd-dist/target/.
Look at how the reports are integrated in CPDConfiguration.java - you can add your own version of the SimpleRenderer.
Create a feature-request at https://sourceforge.net/p/pmd/bugs/
In Unix, it's possible to create a handle to an anonymous file by, e.g., creating and opening it with creat() and then removing the directory link with unlink() - leaving you with a file with an inode and storage but no possible way to re-open it. Such files are often used as temp files (and typically this is what tmpfile() returns to you).
My question: is there any way to re-attach a file like this back into the directory structure? If you could do this it means that you could e.g. implement file writes so that the file appears atomically and fully formed. This appeals to my compulsive neatness. ;)
When poking through the relevant system call functions I expected to find a version of link() called flink() (compare with chmod()/fchmod()) but, at least on Linux this doesn't exist.
Bonus points for telling me how to create the anonymous file without briefly exposing a filename in the disk's directory structure.
A patch for a proposed Linux flink() system call was submitted several years ago, but when Linus stated "there is no way in HELL we can do this securely without major other incursions", that pretty much ended the debate on whether to add this.
Update: As of Linux 3.11, it is now possible to create a file with no directory entry using open() with the new O_TMPFILE flag, and link it into the filesystem once it is fully formed using linkat() on /proc/self/fd/fd with the AT_SYMLINK_FOLLOW flag.
The following example is provided on the open() manual page:
char path[PATH_MAX];
fd = open("/path/to/dir", O_TMPFILE | O_RDWR, S_IRUSR | S_IWUSR);
/* File I/O on 'fd'... */
snprintf(path, PATH_MAX, "/proc/self/fd/%d", fd);
linkat(AT_FDCWD, path, AT_FDCWD, "/path/for/file", AT_SYMLINK_FOLLOW);
Note that linkat() will not allow open files to be re-attached after the last link is removed with unlink().
My question: is there any way to re-attach a file like this back into the directory structure? If you could do this it means that you could e.g. implement file writes so that the file appears atomically and fully formed. This appeals to the my compulsive neatness. ;)
If this is your only goal, you can achieve this in a much simpler and more widely used manner. If you are outputting to a.dat:
Open a.dat.part for write.
Write your data.
Rename a.dat.part to a.dat.
I can understand wanting to be neat, but unlinking a file and relinking it just to be "neat" is kind of silly.
This question on serverfault seems to indicate that this kind of re-linking is unsafe and not supported.
Thanks to #mark4o posting about linkat(2), see his answer for details.
I wanted to give it a try to see what actually happened when trying to actually link an anonymous file back into the filesystem it is stored on. (often /tmp, e.g. for video data that firefox is playing).
As of Linux 3.16, there still appears to be no way to undelete a deleted file that's still held open. Neither AT_SYMLINK_FOLLOW nor AT_EMPTY_PATH for linkat(2) do the trick for deleted files that used to have a name, even as root.
The only alternative is tail -c +1 -f /proc/19044/fd/1 > data.recov, which makes a separate copy, and you have to kill it manually when it's done.
Here's the perl wrapper I cooked up for testing. Use strace -eopen,linkat linkat.pl - </proc/.../fd/123 newname to verify that your system still can't undelete open files. (Same applies even with sudo). Obviously you should read code you find on the Internet before running it, or use a sandboxed account.
#!/usr/bin/perl -w
# 2015 Peter Cordes <peter#cordes.ca>
# public domain. If it breaks, you get to keep both pieces. Share and enjoy
# Linux-only linkat(2) wrapper (opens "." to get a directory FD for relative paths)
if ($#ARGV != 1) {
print "wrong number of args. Usage:\n";
print "linkat old new \t# will use AT_SYMLINK_FOLLOW\n";
print "linkat - <old new\t# to use the AT_EMPTY_PATH flag (requires root, and still doesn't re-link arbitrary files)\n";
exit(1);
}
# use POSIX qw(linkat AT_EMPTY_PATH AT_SYMLINK_FOLLOW); #nope, not even POSIX linkat is there
require 'syscall.ph';
use Errno;
# /usr/include/linux/fcntl.h
# #define AT_SYMLINK_NOFOLLOW 0x100 /* Do not follow symbolic links. */
# #define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */
# #define AT_EMPTY_PATH 0x1000 /* Allow empty relative pathname */
unless (defined &AT_SYMLINK_NOFOLLOW) { sub AT_SYMLINK_NOFOLLOW() { 0x0100 } }
unless (defined &AT_SYMLINK_FOLLOW ) { sub AT_SYMLINK_FOLLOW () { 0x0400 } }
unless (defined &AT_EMPTY_PATH ) { sub AT_EMPTY_PATH () { 0x1000 } }
sub my_linkat ($$$$$) {
# tmp copies: perl doesn't know that the string args won't be modified.
my ($oldp, $newp, $flags) = ($_[1], $_[3], $_[4]);
return !syscall(&SYS_linkat, fileno($_[0]), $oldp, fileno($_[2]), $newp, $flags);
}
sub linkat_dotpaths ($$$) {
open(DOTFD, ".") or die "open . $!";
my $ret = my_linkat(DOTFD, $_[0], DOTFD, $_[1], $_[2]);
close DOTFD;
return $ret;
}
sub link_stdin ($) {
my ($newp, ) = #_;
open(DOTFD, ".") or die "open . $!";
my $ret = my_linkat(0, "", DOTFD, $newp, &AT_EMPTY_PATH);
close DOTFD;
return $ret;
}
sub linkat_follow_dotpaths ($$) {
return linkat_dotpaths($_[0], $_[1], &AT_SYMLINK_FOLLOW);
}
## main
my $oldp = $ARGV[0];
my $newp = $ARGV[1];
# link($oldp, $newp) or die "$!";
# my_linkat(fileno(DIRFD), $oldp, fileno(DIRFD), $newp, AT_SYMLINK_FOLLOW) or die "$!";
if ($oldp eq '-') {
print "linking stdin to '$newp'. You will get ENOENT without root (or CAP_DAC_READ_SEARCH). Even then doesn't work when links=0\n";
$ret = link_stdin( $newp );
} else {
$ret = linkat_follow_dotpaths($oldp, $newp);
}
# either way, you still can't re-link deleted files (tested Linux 3.16 and 4.2).
# print STDERR
die "error: linkat: $!.\n" . ($!{ENOENT} ? "ENOENT is the error you get when trying to re-link a deleted file\n" : '') unless $ret;
# if you want to see exactly what happened, run
# strace -eopen,linkat linkat.pl
Clearly, this is possible -- fsck does it, for example. However, fsck does it with major localized file system mojo and will clearly not be portable, nor executable as an unprivileged user. It's similar to the debugfs comment above.
Writing that flink(2) call would be an interesting exercise. As ijw points out, it would offer some advantages over current practice of temporary file renaming (rename, note, is guaranteed atomic).
Kind of late to the game but I just found http://computer-forensics.sans.org/blog/2009/01/27/recovering-open-but-unlinked-file-data which may answer the question. I haven't tested it, though, so YMMV. It looks sound.
I have a bunch of SQL in a file, which creates the tables and so forth. The problem is that the .read command simply returns "can't open xxx" when I try to execute it. I've set the permissions to everybody read/write, but that didn't help. I can cat the file from the command line and see it fine.
This is under Mac OS 10.6.3.
Anybody have any idea here? Thanks!
Here's the source code in shell.c, where the sqlite3 utility executes the .read and tries to read the .sql file:
if( c=='r' && strncmp(azArg[0], "read", n)==0 && nArg==2 ){
FILE *alt = fopen(azArg[1], "rb");
if( alt==0 ){
fprintf(stderr,"can't open \"%s\"\n", azArg[1]);
}else{
process_input(p, alt);
fclose(alt);
}
}else
You can see that the utility will print "can't open xxx" only when the call to fopen fails. Pity they don't print errno for you, but this info should really help you narrow down the problem as not specific to sqlite.
You're either specifying the path wrong (try quoting it), you don't have permission, or the file really doesn't exist (meaning that there's something different in how you're using cat and .read, like the current directory is different).
Watch out for the ; at the end. .read does not like ;'s.