I need to trim last 8 character of a file name
Example:
Input -Vignesh.dat12345678
expected o/p : Vignesh.dat
I tried using rev but it didn't worked.
Your question says that you need to remove 5 characters, while the description says 8 !!!
Standard Format-
echo Vignesh.dat12345678 | rev | cut -c X- | rev
Assuming you want to remove 8 characters,
echo Vignesh.dat12345678 | rev | cut -c 9- | rev
The above code will remove last 8 characters. To remove n characters, simply put (n+1) instead of X.
Related
I'm looking to replace a space that always comes after a number with a | in the middle of a pattern. There are also similar patterns later in the line sometimes that I do not wish to replace (see first/second lines in the examples).
example:
12315 asdfea 1 1ffesa
45456 asefasef 1 era
12 asfase
4 4aefs
what I need:
12315|asdfea 1 1ffesa
45456|asefasef 1 era
12|asfase
4|4aefs
I have tried this:
sed 's/\([0-9][ ][a-zA-Z]\)/|/g' file.txt
However this deletes the pattern such that it looks like this:
|sdfea 1 1ffesa
|sefasef 1 era
|sfase
|4aefs
Which is not what I need.
For given sample input/output,
$ sed 's/ /|/' file.txt
12315|asdfea 1 1ffesa
45456|asefasef 1 era
12|asfase
4|4aefs
By default, only first match will be replaced. g modifier will replace all matches
To replace first matched space between a digit and alphabet (matching depends on locale too)
$ sed 's/\([0-9]\) \([a-zA-Z]\)/\1|\2/' file.txt
12315|asdfea 1 1ffesa
45456|asefasef 1 era
12|asfase
4 4aefs
This uses capture group and backreferences. Note that last line is not modified
I've been learning about sed and finding it very useful, but cannot find an answer to this in any of the many guides and examples ... I'd like to insert the filename of a text file, minus its path and extension, into a specific line within the text itself. Possible?
In such cases, the correct starting point should be man pages. Manual of sed does not provide a feature for sed to understand "filename", but sed does support inserting a text before/after a line.
As a result you need to isolate the filename separatelly , store the text to a variable and inject this text after/before the line you wish.
Example:
$ a="/home/gv/Desktop/PythonTests/cpu.sh"
$ a="${a##*/}";echo "$a"
cpu.sh
$ a="${a%.*}"; echo "$a"
cpu
$ cat file1
LOCATION 0 X 0
VALUE 1a 2 3
VALUE 1b 2 3
VALUE 1c 2 3
$ sed "2a $a" file1 # Inject the contents of variable $a after line2
LOCATION 0 X 0
VALUE 1a 2 3
cpu
VALUE 1b 2 3
VALUE 1c 2 3
$ sed "2i $a" file1 # Inject the contetns of variable $a before line2
LOCATION 0 X 0
cpu
VALUE 1a 2 3
VALUE 1b 2 3
VALUE 1c 2 3
$ sed "2a George" file1 #Inject a fixed string "George" after line 2
LOCATION 0 X 0
VALUE 1a 2 3
George
VALUE 1b 2 3
VALUE 1c 2 3
Explanation:
a="${a##*/}" : Removes all chars from the beginning of string up to last found slash / (longer match)
a="${a%.*}" : Remove all chars starting from the end of the string up to the first found dot . (short match) . You can also use %% for the longest found dot.
sed "2a $a" : Insert after line 2 the contents of variable $a
sed "2i $q" : Insert before line 2 the contents of $a
Optionally you can use sed -i to make changes in-place / in file under process
wrt I've been learning about sed then you may have been wasting your time as there isn't a lot TO learn about sed beyond s/old/new. Sure there's a ton of other language constructs and things you could do with sed, but in practice you should avoid them all and simply use awk instead. If you edit your question to include concise, testable sample input and expected output and add an awk tag then we can show you how to do whatever you want to do the right way.
Meanwhile, it sounds like all you need is:
$ cat /usr/tmp/file
a
b
c
d
e
$ awk 'NR==3{print gensub(/.*\//,"",1,FILENAME)} 1' /usr/tmp/file
a
b
file
c
d
e
The above inserts the current file name before line 3 of the open file. It uses GNU awk for gensub(), with other awks you'd just use sub() and a variable.
I want to use sed as a part of the pipeline to preserve just 10 first and 10 last lines of its input. It would not be working on physical files, but just reading from STDIN and outputting to STDOUT. The amount of data in stream is bigger than machine RAM (or its disk space), so it needs to relatively efficient. It also must work in stream mode, without creating temporary files (no writeable filesystems).
Extra bonus if it could display one line instead of all of the middle it deleted:
for example, if I had input lines containing numbers from 1 to 100000, I would need it to output (line with literal <cut> text would be nice, but is optional):
1
2
3
4
5
6
7
8
9
10
<cut>
99991
99992
99993
99994
99995
99996
99997
99998
99999
100000
The best I've come up with is to have it output first 10 lines, and last one 1 line with:
yes ' ' | head -n 100000 |nl | \
sed -e '$q;11,$d'`
which outputs
1
2
3
4
5
6
7
8
9
10
100000
but I need it to output more context (10 lines instead of just 1) at the end of data too.
Update: length of the input stream is unknown and will vary, 100000 above is just an example.
Update: as noted in the question and the tag, I need it in sed, not awk, perl or other programming languages in which it is more easy to accomplish (that requirement, along with no tmp files, is due to fact it is embedded system with limited commands and resources available)
Update: if the input is less then that 10+10 lines, it should ideally just print the whole input
You can try following command:
sed -n 'H; 1,10 { p; b }; g; s/\n[^\n]*//; h; $ { s/\n/<cut>\n/; p }'
sed has two blocks to save content, pattern space and hold space. The first one is used to parse current line, and the second one can be used as a backup. The approach is to save in hold space the last ten lines processed.
H saves every line to hold space, g recover hold space, then remove oldest line and save again to hold space, and in last line ($) print adding your magic word in front of it.
The whole command:
yes ' ' | head -n 100000 |nl|\
sed -n 'H; 1,10 { p; b }; g; s/\n[^\n]*//; h; $ { s/\n/<cut>\n/; p }'
Yields:
1
2
3
4
5
6
7
8
9
10
<cut>
99991
99992
99993
99994
99995
99996
99997
99998
99999
100000
And said that, follow the advice from Ed Morton, because awk is simpler and easier to debug or modify some weeks later.
UPDATE:
You can append to hold space after first ten lines and check if there are more than 10 newline characters in it before removing oldest as FIFO structure:
sed -n '1,10 { p; b }; H; g; /\(\n[^\n]\+\)\{11\}/ s/\n[^\n]*//; h; $ { s/^\n//; p }'
Now it's more challenging to know where to add the <cut> string in the edge case of 20 input lines, but I will leave it as an exercise for you.
sed is for simple substitutions on a single line, that is all. For anything else, including this task, you should be using awk:
$ cat tst.awk
BEGIN { beg=(beg?beg:3); end=(end?end:3) }
NR<=beg
{ rec[(NR-1)%end+1] = $0 }
END {
print "<cut>"
for (i=1;i<=end;i++) {
print rec[(NR+i-1)%end+1]
}
}
$ seq 10 | awk -f tst.awk
1
2
3
<cut>
8
9
10
$ seq 10 | awk -v beg=2 -v end=4 -f tst.awk
1
2
<cut>
7
8
9
10
I see you've added a "it has to be sed" requirement to your question but I'll leave this answer here for future readers looking for a sensible way to perform the task.
This might work for you (GNU sed):
sed '1,10b;:a;$!{N;s/\n/&/10;Ta;D};i\<cut>' file
Print the first 10 lines as normal. Collect the next 11 lines and if it is not the end of file, delete the first of them and repeat always maintaining the last 10 lines. At the end of the file, insert a line containing <cut> and print the remaining 10 lines.
This question already has answers here:
An efficient way to transpose a file in Bash
(33 answers)
Closed 6 years ago.
Given a text file file.txt, transpose its content.
For example, if file.txt has the following content:
name age
alice 21
ryan 30
Output the following:
name alice ryan
age 21 30
With shell utils cut and paste:
for f in 1 2 ; do cut -d ' ' -f $f file.txt ; done | paste -d ' ' - - -
Outputs:
name alice ryan
age 21 30
How it works. The field separator in file.txt is a space, so both cut and paste (which have tab as a default field separator) must use the -d ' ' option. We know in advance there are two columns in file.txt, the for loop therefore requires two passes. Pass #1, cut selects column 1 from file.txt, pass #2, column 2. When the for loop ends, what's fed to the pipe '|' looks like:
name alice ryan age 21 30
Then paste outputs that three at a time (hence the three hyphens).
I used the following awk in order to count all words that appears in field 4
awk '{print $4}' file | awk '{print NF}' | grep -c 1
How we can to the same in sed?
Example of file:
1 2 3 4
1 2
1 2 3 4 5
1 2
1 2 3
1 2 3 4
From file sed should return the results 3 (three words on field 4)
yael
First of all, your awk is quite inefficient. Try this:
awk '$4{c++}END{print c}' file
Why do you want it in sed, BTW? This is what awk does well. If you really want it in sed, I guess something like this:
sed '/^\s*\S*\s*\S*\s*\S*\s*$/d' file | wc -l
awk explanation: In every line where fourth field is non-null, increment c. At the end, print c.
sed explanation: delete each line which matches the regexp. Then with wc count the lines of the sed output. The regexp basically says there can be maximum of two whitespace groups in the line, not counting initial and final ones, which then means there can be at most 3 fields in the line.
cut can also be used:
cut -f 5 -d' ' file | wc -w
Select the 5. column (the first one is empty due to the leading blank). The delimiter is a blank.
This might work for you:
sed 's/ *[^ ]*/&/4;t;d;' file | sed -n '$='