Okay, this is probably an evident thing but it escapes me, as in it could probably be done in a much simpler way that I'm not aware of, so far..
Say there's a "file" and I want to view only what's on line number "X" of that file, what would be the solution?
here's what i can think of:
head -X < file | tail -1
sed -n Xp < file
is there anything else (or any other way) from the standard set of unix/gnu/linux text-tools/utils?
sed -n 'Xp' theFile, where X is your line number and theFile is your file.
in vi:
vi +X filename
in EMACS:
emacs +X filename
in the shell:
nl -ba -nln filename| grep '^X '
you can use context grep cgrep instead of grep to see some lines above and below the matching line..
EXAMPLES:
print just that one line:
$ nl -ba -nln active_record.rb | grep '^111 '
111 module ConnectionAdapters
with context:
$ nl -ba -nln active_record.rb | grep -C 2 '^111 '
109 end
110
111 module ConnectionAdapters
112 extend ActiveSupport::Autoload
113
for context control in grep check man grep :
Context Line Control
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.
-C NUM, -NUM, --context=NUM
Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no effect and a warning is given.
awk one-liner:
awk "NR==$X" file
bash loop:
for ((i=1; i<=X; i++)); do
read l
done < file
echo "$l"
Just use vi
vi file
When in the file type
:X
where X is the line number you want to see
However, the sed -n Xp file is a good way if you really only want to see the one line
Related
I am trying to fetch the output of a variable stored in a file in another shell script.
Example:
cat abc.log
var1=2
var2=2
var3=25
I am writing a script to fetch the value of var3.
Thank you in advance.
awk -F= '$1 ~ /^[[:space:]]*var3/ { print $2 }' abc.log
Set the field delimiter to = and then where the line contains "var3", print the second field.
Alternatively, you could:
source abc.log
and then:
echo $var3
Using sed you can isolate 25 with particularity with:
sed -n '/^[[:space:]]*var3=/s/^[^=]*=//p' file
Explanation
This is the general substitution form s/find/replace/ with a matching expression preceding it. The total form is /match/s/find/replace/. The option -n suppresses the normal printing of pattern-space and the p at the end tells sed to print the line where the match and substitution took place. Specifically,
/match/ locates a line with any number of preceding whitespace characters followed by var3=. The POSIX [:space:] character class matches any whitespace,
the /find/ is all characters anchored from the '^' beginning that are not the [^=] character and then match the literal '=' character, and finally
the /replace/ is the empty-string leaving the 25 alone which is printed.
Example Use/Output
$ sed -n '/^[[:space:]]*var3=/s/^[^=]*=//p' file
25
A grep one-liner, if your grep has support for Perl-compatible regular expressions (the -P option; not all greps support that)
grep -Po '^\s*var3=\K.*' abc.log
or,
grep -Po '^\s*var3=\K.*' abc.log | tail -n1
in order to get the last value of the var3, if multiple var3s is a possibility.
Would like to insert line number at specific location in file
e.g.
apple
ball
should be
(1) apple
(2) ball
Using command
sed '/./=' <FileName>| sed '/./N; s/\n/ /'
It generates
1 Apple
2 Ball
1st solution: This should be an easy task for awk.
awk '{print "("FNR") "$0}' Input_file
2nd solution: With pure sed as per OP's attempt try:
sed '=' Input_file | sed 'N; s/^/(/;s/\n/) /'
Easy to do with perl instead:
perl -ne 'print "($.) $_"' foo.txt
If you want to modify the file in-place instead of just printing out the numbered lines on standard output:
perl -ni -e 'print "($.) $_"' foo.txt
Many ways are there to insert line numbers in a file
some of them are :-
1.Using cat command
cat -n file.txt > newfile.txt
2.Using nl command
nl -b a file.txt
Awk and perl both are very usefull and powerfull. But if, like me, you are reluctant to learn yet another programming language, you can complete this task with the bash commands you probably know already.
With bash you can
increment a sequence number n: $((++n))
read all lines from a file foo into a variable l: while read -r l;do ...;done <foo, where the option -r serves to treat backslashes as just characters.
print formatted output to a line: printf "plain text %i %s\n" number string
Now suppose you want to enclose your sequence number in parentheses, and format them to 8 digits with leading zeroes, then you combine all this to get:
n=0;while read -r l;do printf "(%08i) %s\n" $((++n)) "$l";done <foo >numberedfoo
Note that you do not need to initialize the variable n to use it as a sequence number further on. But if you experiment with this command a few times without reinitializing n, your lines will be numbered from where your previous try stopped incrementing.
Finally, if you don't like the C-like formatting syntax of printf, just use plain echo, and leave the formatting to bash variable expansion. Here is how to format a number like in the command above (do type a space before the -, and a ; before the echo) :
nformat="0000000$n"; echo "(${nformat: -8}) ...";
I haven't found anything that clearly answers my question. Although very close, I think...
I have a file with a line:
# Skipsdata for serienummer 1158
I want to extract the 4 digit number at the end and put it into a variable, this number changes from file to file so I can't just search for "1158". But the "# Skipsdata for serienummer" always remains the same.
I believe that either grep, sed or awk may be the answer but I'm not 100 % clear on their usage.
Using Awk as
numberRequired=$(awk '/# Skipsdata for serienummer/{print $NF}' file)
printf "%s\n" "$numberRequired"
1158
You can use grep with the -o switch, which prints only the matched part instead of the whole line.
Print all numbers at the end of lines from file yourFile
grep -Po '\d+$' yourFile
Print all four digit numbers at the end of lines like described in your question:
grep -Po '^# Skipsdata for serienummer \K\d{4}$' yourFile
-P enables perl style regexes which support \d and especially \K.
\d matches any digit (0-9).
\d{4} matches exactly four digits.
\K lets grep forget the previously matched part, such that only the part afterwards is printed.
There are multiple ways to find your number. Assuming the input data is in a file called inputfile:
mynumber=$(sed -n 's/# Skipsdata for serienummer //p' <inputfile) will print only the number and ignore all the other lines;
mynumber=$(grep '^# Skipsdata for serienummer' inputfile | cut -d ' ' -f 5) will filter the relevant lines first, then only output the 5th field (the number)
Is there a (POSIX command line) way to print all of a file EXCEPT the last n lines? Use case being, I will have multiple files of unknown size, all of which contain a boilerplate footer of a known size, which I want to remove. I was wondering if there is already a utility that does this before writing it myself.
Most versions of head(1) - GNU derived, in particular, but not BSD derived - have a feature to do this. It will show the top of the file except the end if you use a negative number for the number of lines to print.
Like so:
head -n -10 textfile
Probably less efficient than the "wc" + "do the math" + "tail" method, but easier to look at:
tail -r file.txt | tail +NUM | tail -r
Where NUM is one more than the number of ending lines you want to remove, e.g. +11 will print all but the last 10 lines. This works on BSD which does not support the head -n -NUM syntax.
The head utility is your friend.
From the man page of head:
-n, --lines=[-]K
print the first K lines instead of the first 10;
with the leading `-', print all but the last K lines of each file
There's no standard commands to do that, but you can use awk or sed to fill a buffer of N lines, and print from the head once it's full. E.g. with awk:
awk -v n=5 '{if(NR>n) print a[NR%n]; a[NR%n]=$0}' file
cat <filename> | head -n -10 # Everything except last 10 lines of a file
cat <filename> | tail -n +10 # Everything except 1st 10 lines of a file
If the footer starts with a consistent line that doesn't appear elsewhere, you can use sed:
sed '/FIRST_LINE_OF_FOOTER/q' filename
That prints the first line of the footer; if you want to avoid that:
sed -n '/FIRST_LINE_OF_FOOTER/q;p' filename
This could be more robust than counting lines if the size of the footer changes in the future. (Or it could be less robust if the first line changes.)
Another option, if your system's head command doesn't support head -n -10, is to precompute the number of lines you want to show. The following depends on bash-specific syntax:
lines=$(wc -l < filename) ; (( lines -= 10 )) ; head -$lines filename
Note that the head -NUMBER syntax is supported by some versions of head for backward compatibility; POSIX only permits the head -n NUMBER form. POSIX also only permits the argument to -n to be a positive decimal integer; head -n 0 isn't necessarily a no-op.
A POSIX-compliant solution is:
lines=$(wc -l < filename) ; lines=$(($lines - 10)) ; head -n $lines filename
If you need to deal with ancient pre-POSIX shells, you might consider this:
lines=`wc -l < filename` ; lines=`expr $lines - 10` ; head -n $lines filename
Any of these might do odd things if a file is 10 or fewer lines long.
tac file.txt | tail +[n+1] | tac
This answer is similar to user9645's, but it avoids the tail -r command, which is also not a valid option many systems. See, e.g., https://ubuntuforums.org/showthread.php?t=1346596&s=4246c451162feff4e519ef2f5cb1a45f&p=8444785#post8444785 for an example.
Note that the +1 (in the brackets) was needed on the system I tried it on to test, but it may not be required on your system. So, to remove the last line, I had to put 2 in the brackets. This is probably related to the fact that you need to have the last line ending with regular line feed character(s). This, arguably, makes the last line a blank line. If you don't do that, then the tac command will combine the last two lines, so removing the "last" line (or the first to the tail command) will actually remove the last two lines.
My answer should also be the fastest solution of those listed to date for systems lacking the improved version of head. So, I think it is both the most robust and the fastest of all the answers listed.
head -n $((`(wc -l < Windows_Terminal.json)`)) Windows_Terminal.json
This will work on Linux and on MacOs, keep in mind Mac does not support a negative value. so This is quite handy.
n.b : replace Windows_Terminal.json with your file name
It is simple. You have to add + to the number of lines that you wanted to avoid.
This example gives to you all the lines except the first 9
tail -n +10 inputfile
(yes, not the first 10...because it counts different...if you want 10, just type
tail -n 11 inputfile)
Trying to debug an issue with a server and my only log file is a 20GB log file (with no timestamps even! Why do people use System.out.println() as logging? In production?!)
Using grep, I've found an area of the file that I'd like to take a look at, line 347340107.
Other than doing something like
head -<$LINENUM + 10> filename | tail -20
... which would require head to read through the first 347 million lines of the log file, is there a quick and easy command that would dump lines 347340100 - 347340200 (for example) to the console?
update I totally forgot that grep can print the context around a match ... this works well. Thanks!
I found two other solutions if you know the line number but nothing else (no grep possible):
Assuming you need lines 20 to 40,
sed -n '20,40p;41q' file_name
or
awk 'FNR>=20 && FNR<=40' file_name
When using sed it is more efficient to quit processing after having printed the last line than continue processing until the end of the file. This is especially important in the case of large files and printing lines at the beginning. In order to do so, the sed command above introduces the instruction 41q in order to stop processing after line 41 because in the example we are interested in lines 20-40 only. You will need to change the 41 to whatever the last line you are interested in is, plus one.
# print line number 52
sed -n '52p' # method 1
sed '52!d' # method 2
sed '52q;d' # method 3, efficient on large files
method 3 efficient on large files
fastest way to display specific lines
with GNU-grep you could just say
grep --context=10 ...
No there isn't, files are not line-addressable.
There is no constant-time way to find the start of line n in a text file. You must stream through the file and count newlines.
Use the simplest/fastest tool you have to do the job. To me, using head makes much more sense than grep, since the latter is way more complicated. I'm not saying "grep is slow", it really isn't, but I would be surprised if it's faster than head for this case. That'd be a bug in head, basically.
What about:
tail -n +347340107 filename | head -n 100
I didn't test it, but I think that would work.
I prefer just going into less and
typing 50% to goto halfway the file,
43210G to go to line 43210
:43210 to do the same
and stuff like that.
Even better: hit v to start editing (in vim, of course!), at that location. Now, note that vim has the same key bindings!
You can use the ex command, a standard Unix editor (part of Vim now), e.g.
display a single line (e.g. 2nd one):
ex +2p -scq file.txt
corresponding sed syntax: sed -n '2p' file.txt
range of lines (e.g. 2-5 lines):
ex +2,5p -scq file.txt
sed syntax: sed -n '2,5p' file.txt
from the given line till the end (e.g. 5th to the end of the file):
ex +5,p -scq file.txt
sed syntax: sed -n '2,$p' file.txt
multiple line ranges (e.g. 2-4 and 6-8 lines):
ex +2,4p +6,8p -scq file.txt
sed syntax: sed -n '2,4p;6,8p' file.txt
Above commands can be tested with the following test file:
seq 1 20 > file.txt
Explanation:
+ or -c followed by the command - execute the (vi/vim) command after file has been read,
-s - silent mode, also uses current terminal as a default output,
q followed by -c is the command to quit editor (add ! to do force quit, e.g. -scq!).
I'd first split the file into few smaller ones like this
$ split --lines=50000 /path/to/large/file /path/to/output/file/prefix
and then grep on the resulting files.
If your line number is 100 to read
head -100 filename | tail -1
Get ack
Ubuntu/Debian install:
$ sudo apt-get install ack-grep
Then run:
$ ack --lines=$START-$END filename
Example:
$ ack --lines=10-20 filename
From $ man ack:
--lines=NUM
Only print line NUM of each file. Multiple lines can be given with multiple --lines options or as a comma separated list (--lines=3,5,7). --lines=4-7 also works.
The lines are always output in ascending order, no matter the order given on the command line.
sed will need to read the data too to count the lines.
The only way a shortcut would be possible would there to be context/order in the file to operate on. For example if there were log lines prepended with a fixed width time/date etc.
you could use the look unix utility to binary search through the files for particular dates/times
Use
x=`cat -n <file> | grep <match> | awk '{print $1}'`
Here you will get the line number where the match occurred.
Now you can use the following command to print 100 lines
awk -v var="$x" 'NR>=var && NR<=var+100{print}' <file>
or you can use "sed" as well
sed -n "${x},${x+100}p" <file>
With sed -e '1,N d; M q' you'll print lines N+1 through M. This is probably a bit better then grep -C as it doesn't try to match lines to a pattern.
Building on Sklivvz' answer, here's a nice function one can put in a .bash_aliases file. It is efficient on huge files when printing stuff from the front of the file.
function middle()
{
startidx=$1
len=$2
endidx=$(($startidx+$len))
filename=$3
awk "FNR>=${startidx} && FNR<=${endidx} { print NR\" \"\$0 }; FNR>${endidx} { print \"END HERE\"; exit }" $filename
}
To display a line from a <textfile> by its <line#>, just do this:
perl -wne 'print if $. == <line#>' <textfile>
If you want a more powerful way to show a range of lines with regular expressions -- I won't say why grep is a bad idea for doing this, it should be fairly obvious -- this simple expression will show you your range in a single pass which is what you want when dealing with ~20GB text files:
perl -wne 'print if m/<regex1>/ .. m/<regex2>/' <filename>
(tip: if your regex has / in it, use something like m!<regex>! instead)
This would print out <filename> starting with the line that matches <regex1> up until (and including) the line that matches <regex2>.
It doesn't take a wizard to see how a few tweaks can make it even more powerful.
Last thing: perl, since it is a mature language, has many hidden enhancements to favor speed and performance. With this in mind, it makes it the obvious choice for such an operation since it was originally developed for handling large log files, text, databases, etc.
print line 5
sed -n '5p' file.txt
sed '5q' file.txt
print everything else than line 5
`sed '5d' file.txt
and my creation using google
#!/bin/bash
#removeline.sh
#remove deleting it comes move line xD
usage() { # Function: Print a help message.
echo "Usage: $0 -l LINENUMBER -i INPUTFILE [ -o OUTPUTFILE ]"
echo "line is removed from INPUTFILE"
echo "line is appended to OUTPUTFILE"
}
exit_abnormal() { # Function: Exit with error.
usage
exit 1
}
while getopts l:i:o:b flag
do
case "${flag}" in
l) line=${OPTARG};;
i) input=${OPTARG};;
o) output=${OPTARG};;
esac
done
if [ -f tmp ]; then
echo "Temp file:tmp exist. delete it yourself :)"
exit
fi
if [ -f "$input" ]; then
re_isanum='^[0-9]+$'
if ! [[ $line =~ $re_isanum ]] ; then
echo "Error: LINENUMBER must be a positive, whole number."
exit 1
elif [ $line -eq "0" ]; then
echo "Error: LINENUMBER must be greater than zero."
exit_abnormal
fi
if [ ! -z $output ]; then
sed -n "${line}p" $input >> $output
fi
if [ ! -z $input ]; then
# remove this sed command and this comes move line to other file
sed "${line}d" $input > tmp && cp tmp $input
fi
fi
if [ -f tmp ]; then
rm tmp
fi
You could try this command:
egrep -n "*" <filename> | egrep "<line number>"
Easy with perl! If you want to get line 1, 3 and 5 from a file, say /etc/passwd:
perl -e 'while(<>){if(++$l~~[1,3,5]){print}}' < /etc/passwd
I am surprised only one other answer (by Ramana Reddy) suggested to add line numbers to the output. The following searches for the required line number and colours the output.
file=FILE
lineno=LINENO
wb="107"; bf="30;1"; rb="101"; yb="103"
cat -n ${file} | { GREP_COLORS="se=${wb};${bf}:cx=${wb};${bf}:ms=${rb};${bf}:sl=${yb};${bf}" grep --color -C 10 "^[[:space:]]\\+${lineno}[[:space:]]"; }