I need to write a shell script that does the following:
In a given folder with files that fit the pattern: update-8.1.0-v46.sql I need to find the maximum version
I need to write the maximum version I've found into a configuration file
For 1, I've found the following answer: Shell script: find maximum value in a sequence of integers without sorting
The only problem I have is that I can't get down to a list of only the versions,
I tried:
ls | grep -o "update-8.1.0-v\(\d*\).sql"
but I get the entire file name in return and not just the matching part
Any ideas?
Maybe move everything to awk?
I ended up using:
SCHEMA=`ls database/targets/oracle/ | grep -o "update-$VERSION-v.*.sql" | sed "s/update-$VERSION-v\([0-9]*\).sql/\1/p" | awk '$0>x{x=$0};END{print x}'`
based on dreamer's answer
you can use sed for this:
echo "update-8.1.0-v46.sql" | sed 's/update-8.1.0-v\([0-9]*\).sql/\1/p'
The output in this case will be 46
grep isn't really the best tool for extracting captured matches, but you can use look-behind assertions if you switch it to use perl-like regular expressions. Anything in the assertion will not be printed when using the -o flag.
ls | grep -Po "(?<=update-8.1.0-v)\d+"
46
Related
I have a bash variable which has the following content:
SSH exit status 255 for i-12hfhf578568tn
i-12hdfghf578568tn is able to connect
i-13456tg is not able to connect
SSH exit status 255 for 1.2.3.4
I want to search the string starting with i- and then extract only that instance id. So, for the above input, I want to have output like below:
i-12hfhf578568tn
i-12hdfghf578568tn
i-13456tg
I am open to use grep, awk, sed.
I am trying to achieve my task by using following command but it gives me whole line:
grep -oE 'i-.*'<<<$variable
Any help?
You can just change your grep command to:
grep -oP 'i-[^\s]*' <<<$variable
Tested on your input:
$ cat test
SSH exit status 255 for i-12hfhf578568tn
i-12hdfghf578568tn is able to connect
i-13456tg is not able to connect
SSH exit status 255 for 1.2.3.4
$ var=`cat test`
$ grep -oP 'i-[^\s]*' <<<$var
i-12hfhf578568tn
i-12hdfghf578568tn
i-13456tg
grep is exactly what you need for this task, sed would be more suitable if you had to reformat the input and awk would be nice if you had either to reformat a string or make some computation of some fields in the rows, columns
Explanation:
-P is to use perl regex
i-[^\s]* is a regex that will match literally i- followed by 0 to N non space character, you could change the * by a + if you want to impose that there is at least 1 char after the - or you could use {min,max} syntax to impose a range.
Let me know if there is something unclear.
Bonus:
Following the comment of Sundeep, you can use one of the improved versions of the regex I have proposed (the first one does use PCRE and the second one posix regex):
grep -oP 'i-\S*' <<<$var
or
grep -o 'i-[^[:blank:]]*' <<<$var
You could use following too(I tested it with GNU awk):
echo "$var" | awk -v RS='[ |\n]' '/^i-/'
You can also use this code (Tested in unix)
echo $test | grep -o "i-[0-z]*"
Here,
-o # Prints only the matching part of the lines
i-[0-z]* # This regular expression, matches all the alphabetical and numerical characters following 'i-'.
After running an fdisk -l, I want to be able to extract the volume group name to input later in a bash script. Example below:
fdisk -l | grep /dev/mapper/vg_palpatine
Disk /dev/mapper/vg_palpatine-lv_root: 105.1 GB
vgextend /dev/vg_$vg_name $partitioned_drive
I want to extract palpatine out of the fdisk -l output and input it as my $vg_name variable. I've been suggested a few different solutions, like sed, cut and awk, but I don't have much experience with those. How would I go about doing this?
We can whole input string with the volume name only. To do this, we ask sed to replace (s///) regex matching with second expression:
vg_name=$(fdisk -l | grep /dev/mapper/vg_palpatine | sed -rn 's/.*vg_(.+)-lv_root.*/\1/p')
Regex explanation:
.* -> Any number of characters.
vg_(.+)-lv_root -> Capture the volume name as group 1.
We use the .* to match the whole input string, then we use group 1 (\1), which captures the volume name only, as substitution.
Note that if you want to use $vg_name on a different script you need to export it first.
You can use this:
vg_name=$(fdisk -l | grep /dev/mapper/vg_palpatine | sed -n "s/.*\/\(.*\)-.*/\1/p")
vgextend /dev/$vg_name $partitioned_drive
I am looking at this question: https://leetcode.com/problems/valid-phone-numbers/
which asked using a cmd to extract the phone numbers.
I found this command works:
cat file.txt | grep -Eo '^(\([0-9]{3}\) ){1}[0-9]{3}-[0-9]{4}$|^([0-9]{3}-){2}[0-9]{4}$'
while this failed:
cat file.txt | grep -E '(^(\([0-9]{3}\))|^([0-9]{3}-))[0-9]{3}-[0-9]{4}'
I don't know why the second failed. Does it because grep doesn't support OR in a group?
No, it's because you dropped the space, so space in a phone number will no longer be allowed.
Also, the grouping in your regex seems to be off by a whack or two. What are you actually trying to express?
Finally, you have a useless use of cat -- grep can perfectly well read one or more input files without the help of cat.
I am new with shell script.
I need to save the number of files with particular extension(.properties) in a variable using shell script.
I have used
ls |grep .properties$ |wc -l
but this command prints the number of properties files in the folder. How can I assign this value in a variable.
I have tried
count=${ls |grep .properties$ |wc -l}
But it is showing error like:
./replicate.sh: line 57: ${ls |grep .properties$ |wc -l}: bad substitution
What is this type of errors?
Please anyone help me to save the number of particular files in a variable for future use.
You're using the wrong brackets, it should be $() (command output substitution) rather than ${} (variable substitution).
count=$(ls -1 | grep '\.properties$' | wc -l)
You'll also notice I've use ls -1 to force one file per line in case your ls doesn't do this automatically for pipelines, and changed the pattern to match the . correctly.
You can also bypass the grep totally if you use something like:
count=$(ls -1 *.properties 2>/dev/null | wc -l)
Just watch out for "evil" filenames like those with embedded newlines for example, though my ls seems to handle these fine by replacing the newline with a ? character - that's not necessarily a good idea for doing things with files but it works okay for counting them.
There are better tools to use if you have such beasts and you need the actual file name, but they're rare enough that you generally don't have to worry about it.
You could use a loop with globbing:
count=0
for i in *.properties; do
count=$((count+1))
done
If you are using a shell that supports arrays, you can simply capture all such file names
files=( *.properties )
and then determine the number of array elements
count=${#files[#]}
(The above assumes bash; other shells may require slightly different syntax.)
You'd better use find instead of parsing ls. Then, use the var=$(command) syntax to store the value.
var=$(find . -maxdepth 1 -name "*\.properties" | wc -l)
Reference: Why you shouldn't parse the output of ls.
To solve the problem appearing if any file name contains new lines, you can use what chepner suggests in the comments:
var=$(find . -maxdepth 1 -name "*\.properties" -exec 'echo 1' | wc -l)
so that for every match it will print not the name, but any random character (in this case, 1) and then the amount of them will be counted to produce the correct output.
Use:
count=`ls|grep .properties$ | wc -l`
echo $count
You could write your assignment like this:
count=$(ls -q | grep -c '\.properties$')
or
count=$(ls -qA | grep -c '\.properties$')
if you want to include hidden files.
This works with all kind of filenames because we're using ls with q.
Sure it's easier to link to some webpage that tells you to "never parse ls" than to read the ls manual and see there's a q option (and that most implementations default to q if the output is to a terminal device which explains why some people here state their ls seems to handle filenames with newlines just fine by replacing the newline with a ? character).
Let's say that during your workday you repeatedly encounter the following form of columnized output from some command in bash (in my case from executing svn st in my Rails working directory):
? changes.patch
M app/models/superman.rb
A app/models/superwoman.rb
in order to work with the output of your command - in this case the filenames - some sort of parsing is required so that the second column can be used as input for the next command.
What I've been doing is to use awk to get at the second column, e.g. when I want to remove all files (not that that's a typical usecase :), I would do:
svn st | awk '{print $2}' | xargs rm
Since I type this a lot, a natural question is: is there a shorter (thus cooler) way of accomplishing this in bash?
NOTE:
What I am asking is essentially a shell command question even though my concrete example is on my svn workflow. If you feel that workflow is silly and suggest an alternative approach, I probably won't vote you down, but others might, since the question here is really how to get the n-th column command output in bash, in the shortest manner possible. Thanks :)
You can use cut to access the second field:
cut -f2
Edit:
Sorry, didn't realise that SVN doesn't use tabs in its output, so that's a bit useless. You can tailor cut to the output but it's a bit fragile - something like cut -c 10- would work, but the exact value will depend on your setup.
Another option is something like: sed 's/.\s\+//'
To accomplish the same thing as:
svn st | awk '{print $2}' | xargs rm
using only bash you can use:
svn st | while read a b; do rm "$b"; done
Granted, it's not shorter, but it's a bit more efficient and it handles whitespace in your filenames correctly.
I found myself in the same situation and ended up adding these aliases to my .profile file:
alias c1="awk '{print \$1}'"
alias c2="awk '{print \$2}'"
alias c3="awk '{print \$3}'"
alias c4="awk '{print \$4}'"
alias c5="awk '{print \$5}'"
alias c6="awk '{print \$6}'"
alias c7="awk '{print \$7}'"
alias c8="awk '{print \$8}'"
alias c9="awk '{print \$9}'"
Which allows me to write things like this:
svn st | c2 | xargs rm
Try the zsh. It supports suffix alias, so you can define X in your .zshrc to be
alias -g X="| cut -d' ' -f2"
then you can do:
cat file X
You can take it one step further and define it for the nth column:
alias -g X2="| cut -d' ' -f2"
alias -g X1="| cut -d' ' -f1"
alias -g X3="| cut -d' ' -f3"
which will output the nth column of file "file". You can do this for grep output or less output, too. This is very handy and a killer feature of the zsh.
You can go one step further and define D to be:
alias -g D="|xargs rm"
Now you can type:
cat file X1 D
to delete all files mentioned in the first column of file "file".
If you know the bash, the zsh is not much of a change except for some new features.
HTH Chris
Because you seem to be unfamiliar with scripts, here is an example.
#!/bin/sh
# usage: svn st | x 2 | xargs rm
col=$1
shift
awk -v col="$col" '{print $col}' "${#--}"
If you save this in ~/bin/x and make sure ~/bin is in your PATH (now that is something you can and should put in your .bashrc) you have the shortest possible command for generally extracting column n; x n.
The script should do proper error checking and bail if invoked with a non-numeric argument or the incorrect number of arguments, etc; but expanding on this bare-bones essential version will be in unit 102.
Maybe you will want to extend the script to allow a different column delimiter. Awk by default parses input into fields on whitespace; to use a different delimiter, use -F ':' where : is the new delimiter. Implementing this as an option to the script makes it slightly longer, so I'm leaving that as an exercise for the reader.
Usage
Given a file file:
1 2 3
4 5 6
You can either pass it via stdin (using a useless cat merely as a placeholder for something more useful);
$ cat file | sh script.sh 2
2
5
Or provide it as an argument to the script:
$ sh script.sh 2 file
2
5
Here, sh script.sh is assuming that the script is saved as script.sh in the current directory; if you save it with a more useful name somewhere in your PATH and mark it executable, as in the instructions above, obviously use the useful name instead (and no sh).
It looks like you already have a solution. To make things easier, why not just put your command in a bash script (with a short name) and just run that instead of typing out that 'long' command every time?
If you are ok with manually selecting the column, you could be very fast using pick:
svn st | pick | xargs rm
Just go to any cell of the 2nd column, press c and then hit enter
Note, that file path does not have to be in second column of svn st output. For example if you modify file, and modify it's property, it will be 3rd column.
See possible output examples in:
svn help st
Example output:
M wc/bar.c
A + wc/qax.c
I suggest to cut first 8 characters by:
svn st | cut -c8- | while read FILE; do echo whatever with "$FILE"; done
If you want to be 100% sure, and deal with fancy filenames with white space at the end for example, you need to parse xml output:
svn st --xml | grep -o 'path=".*"' | sed 's/^path="//; s/"$//'
Of course you may want to use some real XML parser instead of grep/sed.