Getting permission denied error while executing shell command from ruby console.
And the same shell command is working from shell.
From Shell..
tests#tests-workstation:~$ "`grep '^datadir=' /etc/mysql/my.cnf | cut -f 2 -d '='`/db_backups"
bash: /db_backups: is a directory
tests#tests-workstation:~$
From ruby console..
>> %x["`grep '^datadir=' /etc/mysql/my.cnf | cut -f 2 -d '='`/db_backups"]
sh: /db_backups: Permission denied
=> ""
Any Idea !
You're trying to execute a directory and the shells are saying no; bash says no by saying "/db_backups: is a directory" whereas sh says "/db_backups: Permission denied". If you just execute the backedticked part:
grep '^datadir=' /etc/mysql/my.cnf | cut -f 2 -d '='
You'll almost certainly see no output at all and the reason is probably that your regular expression is too tight, something like this:
grep '^[ ]*datadir[ ]*=' /etc/mysql/my.cnf | cut -f2 -d'='
Would serve you better; the character classes contain a space and a tab.
Now that you're looking for the right things we can move on to why it still won't work. The %x[] quoter tries to execute its argument using the shell. When you feed the backticked grep stuff:
`grep '^[ ]*datadir[ ]*=' /etc/mysql/my.cnf | cut -f2 -d'='`/db_backups
to the shell, you should get a directory name that ends with /db_backups but you can't execute a directory. I think you want this to produce the directory name:
d = %x[echo `grep '^[ ]*datadir[ ]*=' /etc/mysql/my.cnf | cut -f2 -d'='`/db_backups].strip
Note the leading echo and the .strip call on the returned string. The .strip is necessary to remove the newline from what echo produces.
I think you're going through a lot of trouble for something that could easily be done with just a couple lines of Ruby:
dir = nil
File.open('/etc/mysql/my.cnf').each do |line|
if(m = line.match(/^\s*datadir\s*=\s*(\S+)/))
dir = m[1] + '/db_backups'
break
end
end
You could probably tighten that up a bit if you wanted but I think that that's at least less confusing than putting shell backticks inside Ruby backticks.
It looks like you just want to get field 2 from the file. Then just do it in Ruby using split
File.open("file").each do |line|
if line[/^datadir/]
print line.split("=",2)[0]
end
end
There is no need to specifically shell out to call grep. This is inefficient and non-portable
Related
I have a test.txt file with links for example:
google.com?test=
google.com?hello=
and this code
xargs -0 -n1 -a FUZZvul.txt -d '\n' -P 20 -I % curl -ks1L '%/?=DarkLotus' | grep -a 'DarkLotus'
When I type a specific word, such as DarkLotus, in the terminal, it checks the links in the file and it brings me the word which is reflected in the links i provided in the test file
There is no problem here, the problem is that I have many links, and when the result appears in the terminal, I do not know which site reflected the DarkLotus word.
How can i do it?
Try -n option. It shows the line number of file with the matched line.
Best Regards,
Haridas.
I'm not sure what you are up to there, but can you invert it? grep by default prints matching lines. The problem here is you are piping the input from the stdout of the previous commands into grep, and that can lack context at grep. Since you have a file to work with:
$ grep 'DarkLotus' FUZZvul.txt
If your intention is to also follow the link then it might be easier to write a bash script:
#!/bin/bash
for line in `grep 'DarkLotus FUZZvul.txt`
do
link=# extract link from line
echo ${link}
curl -ks1L ${link}
done
Then you could make your script accept user input:
#/bin/bash
word="${0}"
for line in `grep ${word} FUZZvul.txt`
...
and then
$ my_link_getter "DarkLotus"
https://google?somearg=DarkLotus
...
And then you could make the txt file a parameter.
etc.
I am trying to use grep with the pwd command.
So, if i enter pwd, it shows me something like:
/home/hrq/my-project/
But, for purposes of a script i am making, i need to use it with grep, so it only prints what is after hrq/, so i need to hide my home folder always (the /home/hrq/) excerpt, and show only what is onwards (like, in this case, only my-project).
Is it possible?
I tried something like
pwd | grep -ov 'home', since i saw that the "-v" flag would be equivalent to the NOT operator, and combine it with the "-o" only matching flag. But it didn't work.
Given:
$ pwd
/home/foo/tmp
$ echo "$PWD"
/home/foo/tmp
Depending on what it is you really want to do, either of these is probably what you really should be using rather than trying to use grep:
$ basename "$PWD"
tmp
$ echo "${PWD#/home/foo/}"
tmp
Use grep -Po 'hrq/\K.*', for example:
grep -Po 'hrq/\K.*' <<< '/home/hrq/my-project/'
my-project/
Here, grep uses the following options:
-P : Use Perl regexes.
-o : Print the matches only (1 match per line), not the entire lines.
\K : Cause the regex engine to "keep" everything it had matched prior to the \K and not include it in the match. Specifically, ignore the preceding part of the regex when printing the match.
SEE ALSO:
grep manual
perlre - Perl regular expressions
I want to remove an entire line of text from all files in a given directory. I know I can use grep -v foo filename to do this one file at a time. And I know I can use grep -r foo to search recursively through a directory. How do I combine these commands to remove a given line of text from all files in a directory?
The UNIX command to find files is named find, not grep. Forget you ever heard of grep -r as it's just a bad idea, here's the right way to find files and perform some action on them:
find . -type f -print | xargs sed -i '/badline/d'
Try something like:
grep -vlre 'foo' . | xargs sed -i 's/pattern/replacement/g'
Broken down:
grep:
-v 'Inverse match'
-l 'Show filename'
-r 'Search recursively'
-e 'Extended pattern search'
xargs: For each entry perform
sed -i: replace inline
I think this would work:
grep -ilre 'Foo' . | xargs sed -i 'extension' 'Foo/d'
Where 'extension' refers to the addition to the file name. It will make a copy of the original file with the extension you designated and the modified file will have the original filename. I added -i in case you require it to be case insensitive.
modified file1 becomes "file1"
original file1 becomes "file1extension"
invalid command code ., despite escaping periods, using sed
One of the responses suggests that the newer version of sed's -i option in OSX is slightly different so you need to add an extension. The file is being interpreted as a command, which is why you are seeing that error.
I've created a small function to allow me to grep through my command history on zsh. The command history 1 will display the entire command history. And running history 1 | egrep ls shows just those command containing ls.
So my function looks like this:
h() {
if [ -z "$*" ]
then
history 1
else
history 1 | egrep "$#"
fi
}
Unfortunately this only results in the following error message:
$ h ls
egrep: ls: No such file or directory
I'm at a loss as to what is wrong in my script. I've trie both grep and egrep to no avail.
What is the full path of grep or egrep?
It's possible that it's running in an alternate shell which has a different PATH set. Try using an explicit /usr/bin/grep or /usr/bin/egrep and see if that fixes anything.
Create a file history.zsh (slightly changed from the original):
#!/bin/zsh
h() {
if [ -z "$*" ]
then
history
else
history | fgrep "$*"
fi
}
Now source this file (so "h" will be refreshed):
. history.zsh
And call the new function:
$ h ls
30 h ls
31 ls
I've abandoned the function. Further reading on the subject of zsh history lead me to this very elegant solution that meets my needs. https://coderwall.com/p/jpj_6q
In a nutshell you add this to your .zshrc:
autoload -U up-line-or-beginning-search
autoload -U down-line-or-beginning-searc
zle -N up-line-or-beginning-search
zle -N down-line-or-beginning-search
bindkey "^[[A" up-line-or-beginning-search # Up
bindkey "^[[B" down-line-or-beginning-search # Down
Now your history can be searched by entering a partial term and using the up or down arrow keys to walk through the matches from your history file.
I'm grepping through a large pile of code managed by git, and whenever I do a grep, I see piles and piles of messages of the form:
> grep pattern * -R -n
whatever/.git/svn: No such file or directory
Is there any way I can make those lines go away?
You can use the -s or --no-messages flag to suppress errors.
-s, --no-messages suppress error messages
grep pattern * -s -R -n
If you are grepping through a git repository, I'd recommend you use git grep. You don't need to pass in -R or the path.
git grep pattern
That will show all matches from your current directory down.
Errors like that are usually sent to the "standard error" stream, which you can pipe to a file or just make disappear on most commands:
grep pattern * -R -n 2>/dev/null
I have seen that happening several times, with broken links (symlinks that point to files that do not exist), grep tries to search on the target file, which does not exist (hence the correct and accurate error message).
I normally don't bother while doing sysadmin tasks over the console, but from within scripts I do look for text files with "find", and then grep each one:
find /etc -type f -exec grep -nHi -e "widehat" {} \;
Instead of:
grep -nRHi -e "widehat" /etc
I usually don't let grep do the recursion itself. There are usually a few directories you want to skip (.git, .svn...)
You can do clever aliases with stances like that one:
find . \( -name .svn -o -name .git \) -prune -o -type f -exec grep -Hn pattern {} \;
It may seem overkill at first glance, but when you need to filter out some patterns it is quite handy.
Have you tried the -0 option in xargs? Something like this:
ls -r1 | xargs -0 grep 'some text'
Use -I in grep.
Example: grep SEARCH_ME -Irs ~/logs.
I redirect stderr to stdout and then use grep's invert-match (-v) to exclude the warning/error string that I want to hide:
grep -r <pattern> * 2>&1 | grep -v "No such file or directory"
I was getting lots of these errors running "M-x rgrep" from Emacs on Windows with /Git/usr/bin in my PATH. Apparently in that case, M-x rgrep uses "NUL" (the Windows null device) rather than "/dev/null". I fixed the issue by adding this to .emacs:
;; Prevent issues with the Windows null device (NUL)
;; when using cygwin find with rgrep.
(defadvice grep-compute-defaults (around grep-compute-defaults-advice-null-device)
"Use cygwin's /dev/null as the null-device."
(let ((null-device "/dev/null"))
ad-do-it))
(ad-activate 'grep-compute-defaults)
One easy way to make grep return zero status all the time is to use || true
→ echo "Hello" | grep "This won't be found" || true
→ echo $?
0
As you can see the output value here is 0 (Success)