Delete specific line number s from a text file using sed

Question

I want to delete one or more specific line numbers from a file  How would I do this using sed

User · Answer

I would like to propose a generalization with awk.

When the file is made by blocks of a fixed size and the lines to delete are repeated for each block, awk can work fine in such a way

awk '{nl=((NR-1)%2000)+1; if ( (nl<714) || ((nl>1025)&&(nl<1029)) ) print  $0}'
 OriginFile.dat > MyOutputCuttedFile.dat

In this example the size for the block is 2000 and I want to print the lines [1..713] and [1026..1029].

NR is the variable used by awk to store the current line number.
% gives the remainder (or modulus) of the division of two integers;
nl=((NR-1)%BLOCKSIZE)+1 Here we write in the variable nl the line number inside the current block. (see below)
|| and && are the logical operator OR and AND.
print $0 writes the full line

Why ((NR-1)%BLOCKSIZE)+1:
(NR-1) We need a shift of one because 1%3=1, 2%3=2, but 3%3=0.
  +1   We add again 1 because we want to restore the desired order.

+-----+------+----------+------------+
| NR  | NR%3 | (NR-1)%3 | (NR-1)%3+1 |
+-----+------+----------+------------+
|  1  |  1   |    0     |     1      |
|  2  |  2   |    1     |     2      |
|  3  |  0   |    2     |     3      |
|  4  |  1   |    0     |     1      |
+-----+------+----------+------------+

User · Answer

cat foo 1 2 3 4 5   sed -e  2d 4d  foo 1 3 5

User · Answer

If you want to delete lines 5 through 10 and 12   sed -e  5 10d 12d  file   This will print the results to the screen  If you want to save the results to the same file   sed -i bak -e  5 10d 12d  file   This will back the file up to file bak  and delete the given lines   Note  Line numbers start at 1  The first line of the file is 1  not 0

User · Answer

and awk as well  awk  NR     5 10 25     file

User · Answer

You can delete a particular single line with its line number by sed -i  33d  file  This will delete the line on 33 line number and save the updated file

User · Answer

This is very often a symptom of an antipattern  The tool which produced the line numbers may well be replaced with one which deletes the lines right away  For example   grep -nh error logfile   cut -d  -f1   deletelines logfile    where deletelines is the utility you are imagining you need  is the same as  grep -v error logfile   Having said that  if you are in a situation where you genuinely need to perform this task  you can generate a simple sed script from the file of line numbers   Humorously  but perhaps slightly confusingly  you can do this with sed   sed  s   d   linenumbers   This accepts a file of line numbers  one per line  and produces  on standard output  the same line numbers with d appended after each   This is a valid sed script  which we can save to a file  or  on some platforms  pipe to another sed instance   sed  s   d   linenumbers   sed -f - logfile   On some platforms  sed -f does not understand the option argument - to mean standard input  so you have to redirect the script to a temporary file  and clean it up when you are done  or maybe replace the lone dash with  dev stdin or  proc  pid fd 1 if your OS  or shell  has that   As always  you can add -i before the -f option to have sed edit the target file in place  instead of producing the result on standard output  On  BSDish platforms  including OSX  you need to supply an explicit argument to -i as well  a common idiom is to supply an empty argument  -i

[unix] Delete specific line number(s) from a text file using sed?

Examples related to unix

Examples related to sed

Examples related to line-numbers