Trying to grep with patterns from one file and use them on a big one file and then save results to files with pattern name and grep output inside, does not work, empty files created.
What I am doing wrong?
while read p; do
grep $p big.txt >>$p
done < patterns.txt
As indicated in comments, you'd better quote the variables so that strange characters in the patterns.txt file will be treated as text:
while IFS= read -r p; do
grep "$p" big.txt >> "$p"
done < patterns.txt
See Read a file line by line assigning the value to a variable for an explanation on IFS= and read -r.
Related
Content of testfile.txt
/path1/abc.txt
/path2/abc.txt.1
/path3/abc.txt123
Content of pattern.txt
abc.txt$
Bash Command
grep -i -f pattern.txt testfile.txt
Output:
/path1/abc.txt
This is a working solution, but currently the $ in the pattern is manually added to each line and this edited pattern file is uploaded to users. I am trying to avoid the manual amendment.
Alternate solution to loop and read line by line, but required scripting skills or upload scripts to user environment.
Want to keep the original pattern files in an audited environment, users just login and run simple cut-n-paste commands.
Any one liner solution?
You can use sed to add $ to pattern.txt and then use grep, but you might run into issues due to regexp metacharacters like the . character. For example, abc.txt$ will also match abc1txt. And unless you take care of matching only the basename from the file path, abc.txt$ will also match /some/path/foobazabc.txt.
I'd suggest to use awk instead:
$ awk '!f{a[$0]; next} $NF in a' pattern.txt f=1 FS='/' testfile.txt
/path1/abc.txt
pattern.txt f=1 FS='/' testfile.txt here a flag f is set between the two files and field separator is also changed to / for the second file
!f{a[$0]; next} if flag f is not set (i.e. for the first file), build an array a with line contents as the key
$NF in a for the second file, if the last field matches a key in array a, print the line
Just noticed that you are also using -i option, so use this for case insensitive matching:
awk '!f{a[tolower($0)]; next} tolower($NF) in a'
Since pattern.txt contains only a single pattern, and you don't want to change it, since it is an audited file, you could do
grep -i -f "$(<pattern.txt)'$' testfile.txt
instead. Note that this would break, if the maintainer of the file one day decided to actually write there a terminating $.
IMO, it would make more sense to explain to the maintainer of pattern.txt that he is supposed to place there a simple regular expression, which is going to match your testfile. In this case s/he can decide whether the pattern really should match only the right edge or some inner part of the lines.
If pattern.txt contains more than one line, and you want to add the $ to each line, you can likewise do a
grep -i -f <(sed 's/$/$/' <pattern.txt) testfile.txt
As the '$' symbol indicates pattern end. The following script should work.
#!/bin/bash
file_pattern='pattern.txt' # path to pattern file
file_test='testfile.txt' # path to test file
while IFS=$ read -r line
do
echo "$line"
grep -wn "$line" $file_test
done < "$file_pattern"
You can remove the IFS descriptor if the pattern file comes with leading/trailing spaces.
Also the grep option -w matches only whole word and -n provides with line number.
I am trying to search inside a folder containing several files. The name of the files is written in upper case with a .sub extension in lower case:
AAA.sub
BBB.sub
CCC.sub
DDD.sub
I am searching a pattern trough those file using grep, however i would like to only use lower case letter for the input files.
In the man page for grep it is written:
-i, --ignore-case
Ignore case distinctions in both the PATTERN and the input files. (-i is specified by POSIX.)
So, if i understood properly:
grep -i subckt /schematics/aaa
and
grep -i subckt /schematics/AAA
Are supposed to both be able to search a pattern "subckt" in the file "aaa" regardless of its case (AAA or aaa) and if two files named aaa and AAA are present at the same time in the foler, i expect grep to search trough both of them.
However when i try my search with the 1st instruction (lower case) it does not work, giving me "no such file or directory" message.
When i try to search with the 2nd instruction (upper case) it works properly.
I obviously understood something wrong about how the -i option with grep, can anyone give me an answer regarding this matter?
Is it possible to be case insensitive with the input files when using grep?
EDIT:
My question was lacking details, even tough i have found the answer to my problem i will add the details in case someone else stumbles upon this:
I have one file that contains a list of each file name i want to grep. My list looks like this:
aaa capacitor C_0
bbb capacitor C_0
ccc resistor R_in
...
The grep is done inside a perl script, the perl script parses the list file and gets the name of each individual file name (aaa bbb ccc) inside a while loop.
However the name inside the list file is written in lower case whereas the name of the files i want to grep is written in upper case.
This is why i wanted to have the input file search to be case insensitive so that i could directly do a grep -i subck aaa and it would search inside the file 'AAA'
However, since the grep is launched from a perl script, and since it is apparently not possible to have grep behave like that, i used the uc() function of perl to convert aaa to AAA and do my grep with it. (see my answer below)
-i affects how the contents are searched, not the name of the files.
When the man page says "Ignore case distinctions in both the PATTERN and the input files." that really means that case is ignored in the pattern ( searching for AAA and aaa are equivalent) and the contents of the input files (a line would match if it includes "AAA" or "aaa" or even "AaA")
I think you want to either list all the filenames on the command line, or find a glob (i.e. wildcard) that matches all the filenames:
grep -i subckt *.sub
In Unix/Linux shells (bash, zsh, and so on) "*" is processed by the shell (bash) not the command (grep). The command receives the list of files and actually can't tell the difference between whether a user typed "grep foo *" and "grep foo file1 file2 file3" (if the directory includes those 3 files)
Please try the following command
find . -iname aaa.sub | grep -rn subckt
find with -iname option will list out files ignoring their case. In the above case find . -iname will list out both aaa.sub & AAA.sub. The output is piped to the grep command.
I have found a way to circumvent my problem by using the uc (upper case) function of perl to convert the input files for the grep function into upper case.
The grep command was launched from a perl script in the first place:
grep -i subckt /schematics/aaa
So, i just did that in my perl script:
$tmp=aaa
$tmp=uc($tmp)
grep -i subckt /schematics/$tmp
Now, the "aaa" name is just an example. In the perl script it is recovered from another parsed file that is written in lower case.
Thanks for the answers tough.
grep uses the filenames as they are listed on the command line. The -i option affects the contents of the files, not the names of the files.
You can use find to select filenames to be searched. The -iname option lets you match files ignoring case.
grep subckt $(find /schematics -iname aaa.sub -print)
If you have many filenames, or those filenames include spaces or other characters that would confuse the shell, the safe and secure way to do this is using the -print0 and -0 options:
find /schematics -iname aaa.sub -print0 | xargs -r -0 grep -i subckt
I have a list of patterns which i want to search in a file and find out which patterns are not matching. How to make grep print some error message or the unmatched pattern to know that pattern doesnt exist?
grep "Macro ABC" base.txt
This doesn't return anything as the pattern doesn't exist in base.txt.
You could use bash for this. If you have all your patterns in a file, you could read that file and check if the pattern is matched in your base file:
FILENAME=patterns.txt
while read -r pattern
do
if ! grep "$pattern" base.txt; then
echo "This doesn't return anything as $pattern doesn't exist in base.txt"
fi
done < "$FILENAME"
cat file.txt | grep -x "\d*"
grep: \Documents and Settings: Is a directory
I want to search file.txt for any lines that are numbers only but grep seems to be viewing \d* as a wildcard for files and not the pattern. How can I specify that it's the pattern and it should use stdin for what to grep over?
The file is full of lines of datetime stamps, some end with a letter, some don't.
20140110122200
20131208041510M
...
I'm trying to only get the lines that don't end in a letter.
EDIT: I've also tried setting the filename instead of piping it with cat. Not much different.
C:\long\path>grep -ex "\d*" -f file.txt
grep: \Dell: Is a directory
grep: \Documents and Settings: Is a directory
Why are you using cat to pass the file to grep? Why not just give grep the filename directly?
grep -x '\d*' file.txt
I think the actual problem you're seeing is that the * wildcard is being expanded. That's why grep is giving you errors that mention actual directories (beginning with 'd') on your system.
Okay I have a file that contains numbers like this:
L21479
What I am trying to do is use grep (or a similar tool) to find all the strings in a file that have the format:
L#####
The # will be the number. SO an L followed by 5 numbers.
Is this even possible in grep? Should I load the file and perform regex?
You can do this with grep, for example with the following command:
grep -E -o 'L[0-9]{5}' name_of_file
For example, given a file with the text:
kasdhflkashl143112343214L232134614
3L1431413543454L2342L3523269ufoidu
gl9983ugsdu8768IUHI/(JHKJASHD/(888
The command above will output:
L23213
L14314
L35232
If it is just in a single file, you can do something along the lines of:
grep -e 'L[0-9]{5}' filename
If you need to search all files in a directory for these strings:
find . -type f | xargs grep -e 'L[0-9]{5}'