It's a well-known task, simple to describe:
Given a text file foo.txt, and a blacklist file of exclusion strings, one per line, produce foo_filtered.txt that has only the lines of foo.txt that do not contain any exclusion string.
A common application is filtering compiler warnings from a build log, but to ignore warnings on files that are not yours. The file foo.txt is the warnings file (itself filtered from the build log), and a blacklist file excluded_filenames.txt with file names, one per line.
I know how it's done in procedural languages like Perl or AWK, and I've even done it with combinations of Linux commands such as cut, comm, and sort.
But I feel that I should be really close with xargs, and just can't see the last step.
I know that if excluded_filenames.txt has only 1 file name in it, then
grep -v foo.txt `cat excluded_filenames.txt`
will do it.
And I know that I can get the filenames one per line with
xargs -L1 -a excluded_filenames.txt
So how do I combine those two into a single solution, without explicit loops in a procedural language?
Looking for the simple and elegant solution.
You should use the -f option (or you can use fgrep which is the same):
grep -vf excluded_filenames.txt foo.txt
You could also use -F which is more directly the answer to what you asked:
grep -vF "`cat excluded_filenames.txt`" foo.txt
from man grep
-f FILE, --file=FILE
Obtain patterns from FILE, one per line. The empty file contains zero patterns, and therefore matches nothing.
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be matched.
Related
I am following the example in this post finding contents of one file into another file in unix shell script but want to print out differently.
Basically file "a.txt", with the following lines:
alpha
0891234
beta
Now, the file "b.txt", with the lines:
Alpha
0808080
0891234
gamma
I would like the output of the command is:
alpha
beta
The first one is "incorrect case" and second one is "missing from b.txt". The 0808080 doesn't matter and it can be there.
This is different from using grep -f "a.txt" "b.txt" and print out 0891234 only.
Is there an elegant way to do this?
Thanks.
Use grep with following options:
grep -Fvf b.txt a.txt
The key is to use -v:
-v, --invert-match
Invert the sense of matching, to select non-matching lines.
When reading patterns from a file I recommend to use the -F option as long as you not explicitly want that patterns are treated as regular expressions.
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings (instead of regular expressions), separated by newlines, any of which
is to be matched.
I need to find a string in a textfile, delete the line containing it, and save the file. The string is found (read from) another textfile, containing hundreds of different strings, one per row. The process is to go on from the first to the last string in the file.
Any (hopefully easy to use) text editors (on Windows OS) recommended ? To achive the task.
I am not into serious day-to-day editing. So I'd be ever so happy if the task could be accomplished with a easy-to-use but still reliable editor.
Thanks a bunch,
Frank
You can try notepad++ since it has a lot of plugins, also a great search algorithm. I did a similar task where I had to do a lot of search/replace stuff, and used a plugin I dug up from the internet, can't remember the name exactly (try google-ing I think it's replaacc for notepad++ or something similar).
On unix/linux/cygwin:
grep -v -f pattern_file unmodified_file > new_file
Remove all lines containing the patterns in pattern_file from unmodified_file, write to new_file.
grep -v outputs lines not matching any pattern. -f reads patterns from a file.
On windows this appears equivalent to running this at the command prompt:
FINDSTR /V /G:pattern_file unmodified_file > new_file
That's it. If you already have the two source files, it's a one-liner.
pattern_file is going to be whitespace and case sensitive unless you delve into other options, which are described with FINDSTR /?
Using sed:
sed -n '/PATTERN/n;p' FILE > FILE.new # then copy FILE.new to FILE
Tells sed to not output anything by default (-n), find the pattern (/PATTERN/) and skip this line if found (n), otherwise print the line (;p). If you have GNU sed you do can just call
sed -i -n '/PATTERN/n;p' FILE`
which automatically updates the file due to (-i /--in-place).
I have some files with the text:
xxxxx
xxxxx
<cert>
</cert>
some other stuff
How can I search with grep and ignore the line returns?
I have many files in the same folder.
I have tried this but it does not seem to stop running:
tr '\n' ' ' | grep '<cert></cert>' *
That is searching for a multi-line pattern, which the usual grep does not appear to support. There are alternative tools, e.g.,
How can I search for a multiline pattern in a file?, which suggests pcregrep, or custom awk, perl scripts.
How can I “grep” patterns across multiple lines?, again suggesting pcregrep (as well as sed scripts).
However, GNU grep is said to support this as well:
How do I grep for multiple patterns on multiple lines? gives as an example
grep -Pzo "^begin\$(.|\n)*^end$" file
to use a newline in a pattern. The options used however include the "experimental" -P which may make it less suitable than pcregrep:
-P, --perl-regexp
Interpret PATTERN as a Perl regular expression. This is highly
experimental and grep -P may warn of unimplemented features.
-z, --null-data
Treat the input as a set of lines, each terminated by a zero
byte (the ASCII NUL character) instead of a newline. Like the
-Z or --null option, this option can be used with commands like
sort -z to process arbitrary file names.
-o, --only-matching
Print only the matched (non-empty) parts of a matching line,
with each such part on a separate output line.
Some experimental options are useful, others less so. This one was noted as the source of problems in Searching for non-ascii characters.
I have a huge SQL file that gets executed on the server. The dump is from my machine and in it there are a few settings relating to my machine. So basically, I want every occurance of "c://temp" to be replace by "//home//some//blah"
How can this be done from the command line?
sed is a good choice for large files.
sed -i.bak -e 's%C://temp%//home//some//blah%' large_file.sql
It is a good choice because doesn't read the whole file at once to change it. Quoting the manual:
A stream editor is used to perform
basic text transformations on an input
stream (a file or input from a
pipeline). While in some ways similar
to an editor which permits scripted
edits (such as ed), sed works by
making only one pass over the
input(s), and is consequently more
efficient. But it is sed's ability to
filter text in a pipeline which
particularly distinguishes it from
other types of editors.
The relevant manual section is here. A small explanation follows
-i.bak enables in place editing leaving a backup copy with .bak extension
s%foo%bar% uses s, the substitution command, which
substitutes matches of first string
in between the % sign, 'foo', for the second
string, 'bar'. It's usually written as s//
but because your strings have plenty
of slashes, it's more convenient to
change them for something else so you
avoid having to escape them.
Example
vinko#mithril:~$ sed -i.bak -e 's%C://temp%//home//some//blah%' a.txt
vinko#mithril:~$ more a.txt
//home//some//blah
D://temp
//home//some//blah
D://temp
vinko#mithril:~$ more a.txt.bak
C://temp
D://temp
C://temp
D://temp
Just for completeness. In place replacement using perl.
perl -i -p -e 's{c://temp}{//home//some//blah}g' mysql.dmp
No backslash escapes required either. ;)
Try sed? Something like:
sed 's/c:\/\/temp/\/\/home\/\/some\/\/blah/' mydump.sql > fixeddump.sql
Escaping all those slashes makes this look horrible though, here's a simpler example which changes foo to bar.
sed 's/foo/bar/' mydump.sql > fixeddump.sql
As others have noted, you can choose your own delimiter, which would prevent the leaning toothpick syndrome in this case:
sed 's|c://temp\\|home//some//blah|' mydump.sql > fixeddump.sql
The clever thing about sed is that it operating on a stream rather than a file all at once, so you can process huge files using only a modest amount of memory.
There's also a non-standard UNIX utility, rpl, which does the exact same thing that the sed examples do; however, I'm not sure whether rpl operates streamwise, so sed may be the better option here.
The sed command can do that.
Rather than escaping the slashes, you can choose a different delimiter (_ in this case):
sed -e 's_c://temp/_/home//some//blah/_' file1.txt > file2.txt
perl -pi -e 's#c://temp#//home//some//blah#g' yourfilename
The -p will treat this script as a loop, it will read the specified file line by line running the regex search and replace.
-i This flag should be used in conjunction with the -p flag. This commands Perl to edit the file in place.
-e Just means execute this perl code.
Good luck
gawk
awk '{gsub("c://temp","//home//some//blah")}1' file
I have a set of 10 CSV files, which normally have a an entry of this kind
a,b,c,d
d,e,f,g
Now due to some error entries in this file have become of this kind
a,b,c,d
d,e,f,g
,,,
h,i,j,k
Now I want to remove the line with only commas in all the files. These files are on a Linux filesystem.
Any command that you recommend that can replaces the erroneous lines in all the files.
It depends on what you mean by replace. If you mean 'remove', then a trivial variant on #wnoise's solution is:
grep -v '^,,,$' old-file.csv > new-file.csv
Note that this deletes just those lines with exactly three commas. If you want to delete mal-formed lines with any number of commas (including zero) - and no other characters on the line, then:
grep -v '^,*$' ...
There are endless other variations on the regex that would deal with other scenarios. Dealing with full CSV data with commas inside quotes starts to need something other than a regex machine. It can be done, within broad limits, especially in more complex regex systems such as PCRE or Perl. But it requires more work.
Check out Mastering Regular Expressions.
sed 's/,,,/replacement/' < old-file.csv > new-file.csv
optionally followed by
mv new-file.csv old-file.csv
Replace or remove, your post is not clear... For replacement see wnoise's answer. For removing, you could use
awk '$0 !~ /,,,/ {print}' <old-file.csv > new-file.csv
What about trying to keep only lines which are matching the desired format instead of handling one exception ?
If the provided input is what you really want to match:
grep -E '[a-z],[a-z],[a-z],[a-z]' < oldfile.csv > newfile.csv
If the input is different, provide it, the regular expression should not be too hard to write.
Do you want to replace them with something, or delete them entirely? Either way, it can be done with sed. To delete:
sed -i -e '/^,\+$/ D' yourfile1.csv yourfile2.csv ...
To replace: well, see wnoise's answer, or if you don't want to create new files with the output,
sed -i -e '/^,\+$/ s//replacement/' yourfile1.csv yourfile2.csv ...
or
sed -i -e '/^,\+$/ c\
replacement' yourfile1.csv yourfile2.csv ...
(that should be entered exactly as is, including the line break). Of course, you can also do this with awk or perl or, if you're only deleting lines, even grep:
egrep -v '^,+$' < oldfile.csv > newfile.csv
I tested these to make sure they work, but I'd advise you to do the same before using them (just in case). You can omit the -i option from sed, in which case it'll print out the results (rather than writing them back to the file), or omit the output redirection >newfile.csv from grep.
EDIT: It was pointed out in a comment that some features of these sed commands only work on GNU sed. As far as I can tell, these are the -i option (which can be replaced with shell redirection, sed ... <infile >outfile ) and the \+ modifier (which can be replaced with \{1,\} ).
Most simply:
$ grep -v ,,,, oldfile > newfile
$ mv newfile oldfile
yes, awk or grep are very good option if you are working in linux platform. However you can use perl regex for other platform. using join & split options.