How to read a file backwards on Linux?

Question

I know that I can use cat to print all content from a file from beginning to end on Linux. Is there a way for doing that backward (last line first)?

Solution 1

sed '1!G;h;$!d' file

sed -n '1!G;h;$p' file

perl -e 'print reverse <>' file

awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' file

Solution 2

Yes, you can use "tac" command.

From man tac:

Usage: tac [OPTION]... [FILE]...
Write each FILE to standard output, last line first.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -b, --before             attach the separator before instead of after
  -r, --regex              interpret the separator as a regular expression
  -s, --separator=STRING   use STRING as the separator instead of newline
      --help     display this help and exit
      --version  output version information and exit

Solution 3

tac is one way, but not default available on all linux.

awk could do it like:

awk '{a[NR]=$0}END{for(i=NR;i>=1;i--)print a[i]}' file

Comments

[Paul Turner]

What do you mean by "read"? Be specific about the content of the file and what you expect a "backwards" result to look like.

[bobef]

I wanted to look at the end of 2gb file, all 2gb on a single line, so I did this "dd if=file.xml ibs=1 skip=2049186000 count=100" - meaning to read 100 bytes starting from position 2049186000. The output has some dd stuff in it but it does the job.