Print a File, Skipping the First X Lines, in Bash

Print a file, skipping the first X lines, in Bash

You'll need tail. Some examples:

$ tail great-big-file.log
< Last 10 lines of great-big-file.log >

If you really need to SKIP a particular number of "first" lines, use

$ tail -n +<N+1> <filename>
< filename, excluding first N lines. >

That is, if you want to skip N lines, you start printing line N+1. Example:

$ tail -n +11 /tmp/myfile
< /tmp/myfile, starting at line 11, or skipping the first 10 lines. >

If you want to just see the last so many lines, omit the "+":

$ tail -n <N> <filename>
< last N lines of file. >

How to skip a line every two lines starting by skipping the first line?

You have to invert your sed command: it should be n;p instead of p;n:

Your code:

for x in {1..20}; do echo $x ; done | sed -n 'p;n'

1
3
5
7
9
11
13
15
17
19

The version with sed inverted:

for x in {1..20}; do echo $x ; done | sed -n 'n;p'

Output:

2
4
6
8
10
12
14
16
18
20

Skip first match in file using Bash

You can add a variable firstline (init it as true).
When you have sn and descr matched, set the var to false, else print.

EDIT: Alternative.

You can use tr and sed for manipulting the file.

First make sure that all lines (except the first) start with DESCR:

tr -d "\n" < file | sed 's/DESCR/\n&/g; $ s/$/\n/'

The first line is without DESCR, the second one is the one you want to ignore.

So process this stream from the third line:

tr -d "\n" < file | sed 's/DESCR/\n&/g; $ s/$/\n/' |
   sed -rn '3,$ s/DESCR: "([^"]+).*SN: ([^[:space:]]+).*/\1,\2/p' 

unix split skip first n of lines

Use tail -n +1001 to get lines starting from 1001st line:

cat *.txt | tail -n +1001 | split --lines=1000

How to print the first line of multiple files?

I'm guessing your version of head doesn't support the -q option; what does man head (run on your Mac) show?

A small awk solution:

awk '{ print ; nextfile}' *

As a file is processed the first line is printed, then we skip to the next file; net result is that we only print the first line of each file.

Keep in mind this could generate some odd results depending on what matches * ... binary files? directories?

How can I remove the first line of a text file using bash/sed script?

Try tail:

tail -n +2 "$FILE"

-n x: Just print the last x lines. tail -n 5 would give you the last 5 lines of the input. The + sign kind of inverts the argument and make tail print anything but the first x-1 lines. tail -n +1 would print the whole file, tail -n +2 everything but the first line, etc.

GNU tail is much faster than sed. tail is also available on BSD and the -n +2 flag is consistent across both tools. Check the FreeBSD or OS X man pages for more.

The BSD version can be much slower than sed, though. I wonder how they managed that; tail should just read a file line by line while sed does pretty complex operations involving interpreting a script, applying regular expressions and the like.

Note: You may be tempted to use

# THIS WILL GIVE YOU AN EMPTY FILE!
tail -n +2 "$FILE" > "$FILE"

but this will give you an empty file. The reason is that the redirection (>) happens before tail is invoked by the shell:

1. Shell truncates file $FILE
2. Shell creates a new process for tail
3. Shell redirects stdout of the tail process to $FILE
4. tail reads from the now empty $FILE

If you want to remove the first line inside the file, you should use:

tail -n +2 "$FILE" > "$FILE.tmp" && mv "$FILE.tmp" "$FILE"

The && will make sure that the file doesn't get overwritten when there is a problem.

Print first few and last few lines of file through a pipe with ... in the middle

An awk:

awk -v head=2 -v tail=2 'FNR==NR && FNR<=head
FNR==NR && cnt++==head {print "..."}
NR>FNR && FNR>(cnt-tail)' file file

Or if a single pass is important (and memory allows), you can use perl:

perl -0777 -lanE 'BEGIN{$head=2; $tail=2;}
END{say join("\n", @F[0..$head-1],("..."),@F[-$tail..-1]);}' file   

Or, an awk that is one pass:

awk -v head=2 -v tail=2 'FNR<=head
{lines[FNR]=$0}
END{
    print "..."
    for (i=FNR-tail+1; i<=FNR; i++) print lines[i]
}' file

Or, nothing wrong with being a caveman direct like:

head -2 file; echo "..."; tail -2 file

Any of these prints:

1
2
...
9
10

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It terms of efficiency, here are some stats.

For small files (ie, less than 10 MB or so) all these are less than 1 second and the 'caveman' approach is 2 ms.

I then created a 1.1 GB file with seq 99999999 >file

• The two pass awk: 50 secs
• One pass perl: 10 seconds
• One pass awk: 29 seconds
• 'Caveman': 2 MS

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