Without using sed or awk, only cut, how do I get the last field when the number of fields are unknown or change with every line?
You could try something like this:
echo 'maps.google.com' | rev | cut -d'.' -f 1 | rev
Explanation
rev reverses "maps.google.com" to be moc.elgoog.spam
cut uses dot (ie '.') as the delimiter, and chooses the first field, which is moc
lastly, we reverse it again to get com
Use a parameter expansion. This is much more efficient than any kind of external command, cut (or grep) included.
data=foo,bar,baz,qux
last=${data##*,}
See BashFAQ #100 for an introduction to native string manipulation in bash.
It is not possible using just cut. Here is a way using grep:
grep -o '[^,]*$'
Replace the comma for other delimiters.
Explanation:
-o (--only-matching) only outputs the part of the input that matches the pattern (the default is to print the entire line if it contains a match).
[^,] is a character class that matches any character other than a comma.
* matches the preceding pattern zero or more time, so [^,]* matches zero or more non‑comma characters.
$ matches the end of the string.
Putting this together, the pattern matches zero or more non-comma characters at the end of the string.
When there are multiple possible matches, grep prefers the one that starts earliest. So the entire last field will be matched.
Full example:
If we have a file called data.csv containing
one,two,three
foo,bar
then grep -o '[^,]*$' < data.csv will output
three
bar
Without awk ?...
But it's so simple with awk:
echo 'maps.google.com' | awk -F. '{print $NF}'
AWK is a way more powerful tool to have in your pocket.
-F if for field separator
NF is the number of fields (also stands for the index of the last)
There are multiple ways. You may use this too.
echo "Your string here"| tr ' ' '\n' | tail -n1
> here
Obviously, the blank space input for tr command should be replaced with the delimiter you need.
This is the only solution possible for using nothing but cut:
echo "s.t.r.i.n.g." | cut -d'.' -f2-
[repeat_following_part_forever_or_until_out_of_memory:] | cut -d'.' -f2-
Using this solution, the number of fields can indeed be unknown and vary from time to time. However as line length must not exceed LINE_MAX characters or fields, including the new-line character, then an arbitrary number of fields can never be part as a real condition of this solution.
Yes, a very silly solution but the only one that meets the criterias I think.
If your input string doesn't contain forward slashes then you can use basename and a subshell:
$ basename "$(echo 'maps.google.com' | tr '.' '/')"
This doesn't use sed or awk but it also doesn't use cut either, so I'm not quite sure if it qualifies as an answer to the question as its worded.
This doesn't work well if processing input strings that can contain forward slashes. A workaround for that situation would be to replace forward slash with some other character that you know isn't part of a valid input string. For example, the pipe (|) character is also not allowed in filenames, so this would work:
$ basename "$(echo 'maps.google.com/some/url/things' | tr '/' '|' | tr '.' '/')" | tr '|' '/'
the following implements A friend's suggestion
#!/bin/bash
rcut(){
nu="$( echo $1 | cut -d"$DELIM" -f 2- )"
if [ "$nu" != "$1" ]
then
rcut "$nu"
else
echo "$nu"
fi
}
$ export DELIM=.
$ rcut a.b.c.d
d
An alternative using perl would be:
perl -pe 's/(.*) (.*)$/$2/' file
where you may change \t for whichever the delimiter of file is
It is better to use awk while working with tabular data. You don't have to master on command. If it can be achieved by awk, why not use that? I suggest you do not waste your precious time, and use a handful of commands to get the job done.
Example:
# $NF refers to the last column in awk
ll | awk '{print $NF}'
If you have a file named filelist.txt that is a list paths such as the following:
c:/dir1/dir2/file1.h
c:/dir1/dir2/dir3/file2.h
then you can do this:
rev filelist.txt | cut -d"/" -f1 | rev
Adding an approach to this old question just for the fun of it:
$ cat input.file # file containing input that needs to be processed
a;b;c;d;e
1;2;3;4;5
no delimiter here
124;adsf;15454
foo;bar;is;null;info
$ cat tmp.sh # showing off the script to do the job
#!/bin/bash
delim=';'
while read -r line; do
while [[ "$line" =~ "$delim" ]]; do
line=$(cut -d"$delim" -f 2- <<<"$line")
done
echo "$line"
done < input.file
$ ./tmp.sh # output of above script/processed input file
e
5
no delimiter here
15454
info
Besides bash, only cut is used.
Well, and echo, I guess.
choose -1
choose supports negative indexing (the syntax is similar to Python's slices).
I realized if we just ensure a trailing delimiter exists, it works. So in my case I have comma and whitespace delimiters. I add a space at the end;
$ ans="a, b"
$ ans+=" "; echo ${ans} | tr ',' ' ' | tr -s ' ' | cut -d' ' -f2
b
Related
Basically, I have a file formatted like
ABC:123
And I would like to flip the strings around the delimiter, so it would look like this
123:ABC
I would prefer to do this with bash/linux tools.
Thanks for any help!
That's reasonably easy with internal bash commands, assuming two fields, as per the following transcript:
pax:~$ x='abc:123'
pax:~$ echo "${x#*:}:${x%:*}"
123:abc
The first substitution ${x#*:} removes everything from the start up to the colon. The second, ${x%:*}, removes everything from the colon to the end.
Then you just re-join them with the colon in-between.
It doesn't matter for your particular data but % and # use the shortest possible pattern. The %% and ## variants will give you the longest possible pattern (greedy).
As an aside, this is ideal if you doing it for one string at a time since you don't need to kick up an external process to do the work for you. But, if you're processing an entire file, there are better ways to do it, such as with awk:
pax:~$ printf "abc:123\ndef:456\nghi:789\n" | awk -F: '{print $2 FS $1}'
123:abc
456:def
789:ghi
#!/bin/sh -x
var1=$(echo -e 'ABC:123' | cut -d':' -f1)
var2=$(echo -e 'ABC:123' | cut -d':' -f2)
echo -e "${var2}":"${var1}"
I use cut to split the string into two parts, and store both of those parts as variables.
From there, it's possible to use echo to re-arrange the variables as you see fit.
Using sed.
sed -E 's/(.*):(.*)/\2:\1/' file.txt
Using paste and cut with process substitution.
paste -d: <(cut -d : -f2 file.txt) <(cut -d : -f1 file.txt)
A slower/slowest shell solution on large set of data/files.
while IFS=: read -r left rigth; do printf '%s:%s\n' "$rigth" "$left"; done < file.txt
I have the following string that I want to extract name and id from and store them in a variable. This is just an example, the list can be longer but they are separated the same way.
[["freepbx","NEWUPDATES","There are 6 modules available for online upgrades"],["cidlookup","noauth","OpenCNAM Requires Authentication"]]
The id's in the string is freepbx and cidlookup, the names are NEWUPDATES and noauth.
I'd like them to come out like:
freepbx NEWUPDATES
cidlookup noauth
I'm running a program from command line that needs it's input this way.
Any help is greatly appreciated!
This is one way to do it:
echo '[["freepbx","NEWUPDATES","There are 6 modules available for online upgrades"],["cidlookup","noauth","OpenCNAM Requires Authentication"]]' | sed -e 's/\],\[/\n/g' -e 's/\(\[\[\)*"//g' | awk -F ',' '{print $1, $2}'
freepbx NEWUPDATES
cidlookup noauth
Explanation:
The sed command s/\],\[/\n/g will replace all ], [ which separate each record with a new line(\n) character. This will allow you to treat each line as a separate record which makes all other tools much easier:)
The second sed command s/\(\[\[\)*"//g will remove the quotes and the initial [[ at the start of the first record. This cleans up things from your data leaving only the , between your fields.
Finally, awk command -F ',' '{print $1, $2}', the -F tells awk to use the , as field separator (instead of space) and $1 and $2 to print the first and second fields.
awk to the rescue!
$ awk -F'"' -v RS="\\\],\\\[" '{print $2,$4}' file
freepbx NEWUPDATES
cidlookup noauth
If jq is available:
jq -r '.[] | "\(.[0]) \(.[1])"'
Pipe .[] ( all elements in the array) output to print only 0th and 1st element "\(.[0]) \(.[1])"as in desired output.
Without using sed or awk, only cut, how do I get the last field when the number of fields are unknown or change with every line?
You could try something like this:
echo 'maps.google.com' | rev | cut -d'.' -f 1 | rev
Explanation
rev reverses "maps.google.com" to be moc.elgoog.spam
cut uses dot (ie '.') as the delimiter, and chooses the first field, which is moc
lastly, we reverse it again to get com
Use a parameter expansion. This is much more efficient than any kind of external command, cut (or grep) included.
data=foo,bar,baz,qux
last=${data##*,}
See BashFAQ #100 for an introduction to native string manipulation in bash.
It is not possible using just cut. Here is a way using grep:
grep -o '[^,]*$'
Replace the comma for other delimiters.
Explanation:
-o (--only-matching) only outputs the part of the input that matches the pattern (the default is to print the entire line if it contains a match).
[^,] is a character class that matches any character other than a comma.
* matches the preceding pattern zero or more time, so [^,]* matches zero or more non‑comma characters.
$ matches the end of the string.
Putting this together, the pattern matches zero or more non-comma characters at the end of the string.
When there are multiple possible matches, grep prefers the one that starts earliest. So the entire last field will be matched.
Full example:
If we have a file called data.csv containing
one,two,three
foo,bar
then grep -o '[^,]*$' < data.csv will output
three
bar
Without awk ?...
But it's so simple with awk:
echo 'maps.google.com' | awk -F. '{print $NF}'
AWK is a way more powerful tool to have in your pocket.
-F if for field separator
NF is the number of fields (also stands for the index of the last)
There are multiple ways. You may use this too.
echo "Your string here"| tr ' ' '\n' | tail -n1
> here
Obviously, the blank space input for tr command should be replaced with the delimiter you need.
This is the only solution possible for using nothing but cut:
echo "s.t.r.i.n.g." | cut -d'.' -f2-
[repeat_following_part_forever_or_until_out_of_memory:] | cut -d'.' -f2-
Using this solution, the number of fields can indeed be unknown and vary from time to time. However as line length must not exceed LINE_MAX characters or fields, including the new-line character, then an arbitrary number of fields can never be part as a real condition of this solution.
Yes, a very silly solution but the only one that meets the criterias I think.
If your input string doesn't contain forward slashes then you can use basename and a subshell:
$ basename "$(echo 'maps.google.com' | tr '.' '/')"
This doesn't use sed or awk but it also doesn't use cut either, so I'm not quite sure if it qualifies as an answer to the question as its worded.
This doesn't work well if processing input strings that can contain forward slashes. A workaround for that situation would be to replace forward slash with some other character that you know isn't part of a valid input string. For example, the pipe (|) character is also not allowed in filenames, so this would work:
$ basename "$(echo 'maps.google.com/some/url/things' | tr '/' '|' | tr '.' '/')" | tr '|' '/'
the following implements A friend's suggestion
#!/bin/bash
rcut(){
nu="$( echo $1 | cut -d"$DELIM" -f 2- )"
if [ "$nu" != "$1" ]
then
rcut "$nu"
else
echo "$nu"
fi
}
$ export DELIM=.
$ rcut a.b.c.d
d
An alternative using perl would be:
perl -pe 's/(.*) (.*)$/$2/' file
where you may change \t for whichever the delimiter of file is
It is better to use awk while working with tabular data. You don't have to master on command. If it can be achieved by awk, why not use that? I suggest you do not waste your precious time, and use a handful of commands to get the job done.
Example:
# $NF refers to the last column in awk
ll | awk '{print $NF}'
If you have a file named filelist.txt that is a list paths such as the following:
c:/dir1/dir2/file1.h
c:/dir1/dir2/dir3/file2.h
then you can do this:
rev filelist.txt | cut -d"/" -f1 | rev
Adding an approach to this old question just for the fun of it:
$ cat input.file # file containing input that needs to be processed
a;b;c;d;e
1;2;3;4;5
no delimiter here
124;adsf;15454
foo;bar;is;null;info
$ cat tmp.sh # showing off the script to do the job
#!/bin/bash
delim=';'
while read -r line; do
while [[ "$line" =~ "$delim" ]]; do
line=$(cut -d"$delim" -f 2- <<<"$line")
done
echo "$line"
done < input.file
$ ./tmp.sh # output of above script/processed input file
e
5
no delimiter here
15454
info
Besides bash, only cut is used.
Well, and echo, I guess.
choose -1
choose supports negative indexing (the syntax is similar to Python's slices).
I realized if we just ensure a trailing delimiter exists, it works. So in my case I have comma and whitespace delimiters. I add a space at the end;
$ ans="a, b"
$ ans+=" "; echo ${ans} | tr ',' ' ' | tr -s ' ' | cut -d' ' -f2
b
So I have this string:
$var=server#10.200.200.20:/home/some/directory/file
I just want to extract the directory address meaning I only want the bit after the ":" character and get:
/home/some/directory/file
thanks.
I need a generic command so the cut command wont work as the $var variable doesn't have a fixed length.
Using sed:
$ var=server#10.200.200.20:/home/some/directory/file
$ echo $var | sed 's/.*://'
/home/some/directory/file
This might work for you:
echo ${var#*:}
See Example 10-10. Pattern matching in parameter substitution
This will also do.
echo $var | cut -f2 -d":"
For completeness, using cut
cut -d : -f 2 <<< $var
And using only bash:
IFS=: read a b <<< $var ; echo $b
You don't say which shell you're using. If it's a POSIX-compatible one such as Bash, then parameter expansion can do what you want:
Parameter Expansion
...
${parameter#word}
Remove Smallest Prefix Pattern.
The word is expanded to produce a pattern. The parameter expansion then results in parameter, with the smallest portion of the prefix matched by the pattern deleted.
In other words, you can write
$var="${var#*:}"
which will remove anything matching *: from $var (i.e. everything up to and including the first :). If you want to match up to the last :, then you could use ## in place of #.
This is all assuming that the part to remove does not contain : (true for IPv4 addresses, but not for IPv6 addresses)
This should do the trick:
$ echo "$var" | awk -F':' '{print $NF}'
/home/some/directory/file
awk -F: '{print $2}' <<< $var
I'm trying to parse file names in specific directory. Filenames are of format:
token1_token2_token3_token(N-1)_token(N).sh
I need to cut the tokens using delimiter '_', and need to take string except the last two tokens. In above examlpe output should be token1_token2_token3.
The number of tokens is not fixed. I've tried to do it with -f#- option of cut command, but did not find any solution. Any ideas?
With cut:
$ echo t1_t2_t3_tn1_tn2.sh | rev | cut -d_ -f3- | rev
t1_t2_t3
rev reverses each line.
The 3- in -f3- means from the 3rd field to the end of the line (which is the beginning of the line through the third-to-last field in the unreversed text).
You may use POSIX defined parameter substitution:
$ name="t1_t2_t3_tn1_tn2.sh"
$ name=${name%_*_*}
$ echo $name
t1_t2_t3
It can not be done with cut, However, you can use sed
sed -r 's/(_[^_]+){2}$//g'
Just a different way to write ysth's answer :
echo "t1_t2_t3_tn1_tn2.sh" |rev| cut -d"_" -f1,2 --complement | rev