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How to reverse the content of binary file?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ margin-bottom:0;
}

10

1

I was solving a challenge where I found a data file with no file extension. The file command shows that it is a data file (application/octet-stream). The hd command shows GNP. in the last line. So if I reverse this file then I will get the .PNG format file, I searched everywhere but I didn't find a solution explaining how to reverse the content of a binary file.

binary

share|improve this question

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

add a comment | 

10

1

I was solving a challenge where I found a data file with no file extension. The file command shows that it is a data file (application/octet-stream). The hd command shows GNP. in the last line. So if I reverse this file then I will get the .PNG format file, I searched everywhere but I didn't find a solution explaining how to reverse the content of a binary file.

binary

share|improve this question

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

add a comment | 

I was solving a challenge where I found a data file with no file extension. The file command shows that it is a data file (application/octet-stream). The hd command shows GNP. in the last line. So if I reverse this file then I will get the .PNG format file, I searched everywhere but I didn't find a solution explaining how to reverse the content of a binary file.

binary

share|improve this question

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

share|improve this question

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

share|improve this question

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

edited 2 hours ago

Solomon Ucko

10916

edited 2 hours ago

Solomon Ucko

10916

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

asked Jan 11 '18 at 17:44

Prvt_YadvPrvt_Yadv

3,35631531

5 Answers
5

active

oldest

votes

7

With xxd (from vim) and tac (from GNU coreutils, also tail -r on some systems):

< file.gnp xxd -p -c1 | tac | xxd -p -r > file.png

share|improve this answer

edited Jan 12 '18 at 6:53

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Is there any way for this to be combined with vi.stackexchange.com/a/2237/10649? I tried all kind of combinations with no luck :(
  
  – Iulian Onofrei
  May 12 '18 at 17:26
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is not a solution because it will mirror all the file.
  
  – Philippe Delteil
  Nov 21 '18 at 3:33
  

  
  
  
  

add a comment | 

7

With perl:

<file.gnp perl -0777 -F -ape '$_=reverse@F' > file.png

• 
  -a: awk mode were records are split into fields


• 
  -0777 -p: slurp-mode, file read into one $_ record, modified record printed afterwards.


• 
  -F: empty field separator, so fields are individual bytes


• 
  $_=reverse@F: output record is the concatenation of the list of fields (@F) reversed.

share|improve this answer

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

add a comment | 

4

In zsh (the only shell that can internally deal with binary data (unless you want to consider ksh93's base64 encoding approach)):

zmodload zsh/mapfile

(LC_ALL=C; printf %s ${(s::Oa)mapfile[file.gnp]} > file.png)

• 
  LC_ALL=C: characters are bytes


• 
  $mapfile[file.gnp]: content of file.gnp file


• 
  s::: split the string into its byte constituents


• 
  Oa: reverse Order on array subscript that array

share|improve this answer

edited Jan 12 '18 at 14:29

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  zsh is not the only shell that can handle binary data.
  
  – fpmurphy
  Jan 12 '18 at 14:21
  

  
  
  
  

add a comment | 

2

Here is one way of reversing a binary file using ksh93. I have left the code "loose" to make it easier to understand.

#!/bin/ksh93



typeset -b byte



redirect 3< image.gpj || exit 1



eof=$(3<#((EOF)))



read -r -u 3 -N 1 byte

printf "%B" byte > image.jpg

3<#((CUR - 1))



while (( $(3<#) > 0 ))

do

    read -r -u 3 -N 1 byte

    printf "%B" byte >> image.jpg

    3<#((CUR - 2))

done



read -r -u 3 -N 1 byte

printf "%B" byte >> image.jpg



redirect 3<&- || echo 'cannot close FD 3'



exit 0

share|improve this answer

edited Jan 12 '18 at 14:23

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  nice. That's the only answer so far that doesn't involve storing the whole file in memory. However, it's terribly inefficient in that it makes several system calls for each byte of the file (and conversions to/from base64), so wouldn't be suitable for files that don't fit in memory either. On my machine, it processes files at about 10KB/s
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:51
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Note that the first read above should read nothing as it's done at the end of the file.
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:58
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Trying to understand why it was so slow, I tried running it under strace and ksh93 seems to be behaving very weirdly, where it seeks all over the place within the file and reads large amounts at the time. Maybe a variant of github.com/att/ast/issues/15
  
  – Stéphane Chazelas
  Jan 12 '18 at 16:00
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas. No mystery as to why it is relatively slow. Within the loop it has to seek backwards each time it reads a byte. This can easily be significantly reduced by a factor of 20 or even more by reading and writing more than one byte at a time. The write side of things can similarly be optimized. Lots of other techniques are available to further speed things up. I will leave that exercise up to you.
  
  – fpmurphy
  Jan 13 '18 at 5:49
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try strace on the script to see what I mean. ksh93 reads the files thousands of times over. For instance, before reading the first byte, it seeks 64KiB off the end of the file, reads 64KiB, then seeks before the last byte and reads 1 byte and does something similar for every byte. Note that what you can do with those base64 encoded strings is limited, so if you read more than one byte at a time, it's going to be more difficult to extract the individual bytes of that.
  
  – Stéphane Chazelas
  Jan 13 '18 at 9:23
  
  
  

  
  
  
  

add a comment | 

0

I tried the following:

tac -rs '.' input.gnp > output.png

The idea is to force 'tac' using any character as separator.
I tried that on a binary file and it seemed to work but any confirmation would be appreciated.

Main advantage is that it does not load file into memory.

share|improve this answer

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Doesn't work for me (here with GNU tac 8.28) when the input contains newline characters. printf '1n2' | tac -rs . | od -vAn -tc outputs n 2 1 instead of 2 n 1. You'd also need LC_ALL=C or . could match multi-byte characters.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  LC_ALL=C tac -rs $'.\|n' seems to work though.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:25
  

  
  
  
  

add a comment | 

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7

With xxd (from vim) and tac (from GNU coreutils, also tail -r on some systems):

< file.gnp xxd -p -c1 | tac | xxd -p -r > file.png

share|improve this answer

edited Jan 12 '18 at 6:53

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Is there any way for this to be combined with vi.stackexchange.com/a/2237/10649? I tried all kind of combinations with no luck :(
  
  – Iulian Onofrei
  May 12 '18 at 17:26
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is not a solution because it will mirror all the file.
  
  – Philippe Delteil
  Nov 21 '18 at 3:33
  

  
  
  
  

add a comment | 

7

With xxd (from vim) and tac (from GNU coreutils, also tail -r on some systems):

< file.gnp xxd -p -c1 | tac | xxd -p -r > file.png

share|improve this answer

edited Jan 12 '18 at 6:53

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Is there any way for this to be combined with vi.stackexchange.com/a/2237/10649? I tried all kind of combinations with no luck :(
  
  – Iulian Onofrei
  May 12 '18 at 17:26
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is not a solution because it will mirror all the file.
  
  – Philippe Delteil
  Nov 21 '18 at 3:33
  

  
  
  
  

add a comment | 

With xxd (from vim) and tac (from GNU coreutils, also tail -r on some systems):

< file.gnp xxd -p -c1 | tac | xxd -p -r > file.png

share|improve this answer

edited Jan 12 '18 at 6:53

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

< file.gnp xxd -p -c1 | tac | xxd -p -r > file.png

share|improve this answer

edited Jan 12 '18 at 6:53

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:41

Stéphane ChazelasStéphane Chazelas

315k57599957

7

With perl:

<file.gnp perl -0777 -F -ape '$_=reverse@F' > file.png

• 
  -a: awk mode were records are split into fields


• 
  -0777 -p: slurp-mode, file read into one $_ record, modified record printed afterwards.


• 
  -F: empty field separator, so fields are individual bytes


• 
  $_=reverse@F: output record is the concatenation of the list of fields (@F) reversed.

share|improve this answer

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

add a comment | 

7

With perl:

<file.gnp perl -0777 -F -ape '$_=reverse@F' > file.png

• 
  -a: awk mode were records are split into fields


• 
  -0777 -p: slurp-mode, file read into one $_ record, modified record printed afterwards.


• 
  -F: empty field separator, so fields are individual bytes


• 
  $_=reverse@F: output record is the concatenation of the list of fields (@F) reversed.

share|improve this answer

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

add a comment | 

With perl:

<file.gnp perl -0777 -F -ape '$_=reverse@F' > file.png

• 
  -a: awk mode were records are split into fields


• 
  -0777 -p: slurp-mode, file read into one $_ record, modified record printed afterwards.


• 
  -F: empty field separator, so fields are individual bytes


• 
  $_=reverse@F: output record is the concatenation of the list of fields (@F) reversed.

share|improve this answer

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

<file.gnp perl -0777 -F -ape '$_=reverse@F' > file.png

share|improve this answer

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:46

Stéphane ChazelasStéphane Chazelas

315k57599957

4

In zsh (the only shell that can internally deal with binary data (unless you want to consider ksh93's base64 encoding approach)):

zmodload zsh/mapfile

(LC_ALL=C; printf %s ${(s::Oa)mapfile[file.gnp]} > file.png)

• 
  LC_ALL=C: characters are bytes


• 
  $mapfile[file.gnp]: content of file.gnp file


• 
  s::: split the string into its byte constituents


• 
  Oa: reverse Order on array subscript that array

share|improve this answer

edited Jan 12 '18 at 14:29

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  zsh is not the only shell that can handle binary data.
  
  – fpmurphy
  Jan 12 '18 at 14:21
  

  
  
  
  

add a comment | 

4

In zsh (the only shell that can internally deal with binary data (unless you want to consider ksh93's base64 encoding approach)):

zmodload zsh/mapfile

(LC_ALL=C; printf %s ${(s::Oa)mapfile[file.gnp]} > file.png)

• 
  LC_ALL=C: characters are bytes


• 
  $mapfile[file.gnp]: content of file.gnp file


• 
  s::: split the string into its byte constituents


• 
  Oa: reverse Order on array subscript that array

share|improve this answer

edited Jan 12 '18 at 14:29

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  zsh is not the only shell that can handle binary data.
  
  – fpmurphy
  Jan 12 '18 at 14:21
  

  
  
  
  

add a comment | 

In zsh (the only shell that can internally deal with binary data (unless you want to consider ksh93's base64 encoding approach)):

zmodload zsh/mapfile

(LC_ALL=C; printf %s ${(s::Oa)mapfile[file.gnp]} > file.png)

• 
  LC_ALL=C: characters are bytes


• 
  $mapfile[file.gnp]: content of file.gnp file


• 
  s::: split the string into its byte constituents


• 
  Oa: reverse Order on array subscript that array

share|improve this answer

edited Jan 12 '18 at 14:29

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

zmodload zsh/mapfile

(LC_ALL=C; printf %s ${(s::Oa)mapfile[file.gnp]} > file.png)

share|improve this answer

edited Jan 12 '18 at 14:29

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

answered Jan 11 '18 at 21:36

Stéphane ChazelasStéphane Chazelas

315k57599957

2

Here is one way of reversing a binary file using ksh93. I have left the code "loose" to make it easier to understand.

#!/bin/ksh93



typeset -b byte



redirect 3< image.gpj || exit 1



eof=$(3<#((EOF)))



read -r -u 3 -N 1 byte

printf "%B" byte > image.jpg

3<#((CUR - 1))



while (( $(3<#) > 0 ))

do

    read -r -u 3 -N 1 byte

    printf "%B" byte >> image.jpg

    3<#((CUR - 2))

done



read -r -u 3 -N 1 byte

printf "%B" byte >> image.jpg



redirect 3<&- || echo 'cannot close FD 3'



exit 0

share|improve this answer

edited Jan 12 '18 at 14:23

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  nice. That's the only answer so far that doesn't involve storing the whole file in memory. However, it's terribly inefficient in that it makes several system calls for each byte of the file (and conversions to/from base64), so wouldn't be suitable for files that don't fit in memory either. On my machine, it processes files at about 10KB/s
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:51
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Note that the first read above should read nothing as it's done at the end of the file.
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:58
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Trying to understand why it was so slow, I tried running it under strace and ksh93 seems to be behaving very weirdly, where it seeks all over the place within the file and reads large amounts at the time. Maybe a variant of github.com/att/ast/issues/15
  
  – Stéphane Chazelas
  Jan 12 '18 at 16:00
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas. No mystery as to why it is relatively slow. Within the loop it has to seek backwards each time it reads a byte. This can easily be significantly reduced by a factor of 20 or even more by reading and writing more than one byte at a time. The write side of things can similarly be optimized. Lots of other techniques are available to further speed things up. I will leave that exercise up to you.
  
  – fpmurphy
  Jan 13 '18 at 5:49
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try strace on the script to see what I mean. ksh93 reads the files thousands of times over. For instance, before reading the first byte, it seeks 64KiB off the end of the file, reads 64KiB, then seeks before the last byte and reads 1 byte and does something similar for every byte. Note that what you can do with those base64 encoded strings is limited, so if you read more than one byte at a time, it's going to be more difficult to extract the individual bytes of that.
  
  – Stéphane Chazelas
  Jan 13 '18 at 9:23
  
  
  

  
  
  
  

add a comment | 

2

Here is one way of reversing a binary file using ksh93. I have left the code "loose" to make it easier to understand.

#!/bin/ksh93



typeset -b byte



redirect 3< image.gpj || exit 1



eof=$(3<#((EOF)))



read -r -u 3 -N 1 byte

printf "%B" byte > image.jpg

3<#((CUR - 1))



while (( $(3<#) > 0 ))

do

    read -r -u 3 -N 1 byte

    printf "%B" byte >> image.jpg

    3<#((CUR - 2))

done



read -r -u 3 -N 1 byte

printf "%B" byte >> image.jpg



redirect 3<&- || echo 'cannot close FD 3'



exit 0

share|improve this answer

edited Jan 12 '18 at 14:23

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  nice. That's the only answer so far that doesn't involve storing the whole file in memory. However, it's terribly inefficient in that it makes several system calls for each byte of the file (and conversions to/from base64), so wouldn't be suitable for files that don't fit in memory either. On my machine, it processes files at about 10KB/s
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:51
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Note that the first read above should read nothing as it's done at the end of the file.
  
  – Stéphane Chazelas
  Jan 12 '18 at 15:58
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Trying to understand why it was so slow, I tried running it under strace and ksh93 seems to be behaving very weirdly, where it seeks all over the place within the file and reads large amounts at the time. Maybe a variant of github.com/att/ast/issues/15
  
  – Stéphane Chazelas
  Jan 12 '18 at 16:00
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @StéphaneChazelas. No mystery as to why it is relatively slow. Within the loop it has to seek backwards each time it reads a byte. This can easily be significantly reduced by a factor of 20 or even more by reading and writing more than one byte at a time. The write side of things can similarly be optimized. Lots of other techniques are available to further speed things up. I will leave that exercise up to you.
  
  – fpmurphy
  Jan 13 '18 at 5:49
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try strace on the script to see what I mean. ksh93 reads the files thousands of times over. For instance, before reading the first byte, it seeks 64KiB off the end of the file, reads 64KiB, then seeks before the last byte and reads 1 byte and does something similar for every byte. Note that what you can do with those base64 encoded strings is limited, so if you read more than one byte at a time, it's going to be more difficult to extract the individual bytes of that.
  
  – Stéphane Chazelas
  Jan 13 '18 at 9:23
  
  
  

  
  
  
  

add a comment | 

Here is one way of reversing a binary file using ksh93. I have left the code "loose" to make it easier to understand.

#!/bin/ksh93



typeset -b byte



redirect 3< image.gpj || exit 1



eof=$(3<#((EOF)))



read -r -u 3 -N 1 byte

printf "%B" byte > image.jpg

3<#((CUR - 1))



while (( $(3<#) > 0 ))

do

    read -r -u 3 -N 1 byte

    printf "%B" byte >> image.jpg

    3<#((CUR - 2))

done



read -r -u 3 -N 1 byte

printf "%B" byte >> image.jpg



redirect 3<&- || echo 'cannot close FD 3'



exit 0

share|improve this answer

edited Jan 12 '18 at 14:23

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

#!/bin/ksh93



typeset -b byte



redirect 3< image.gpj || exit 1



eof=$(3<#((EOF)))



read -r -u 3 -N 1 byte

printf "%B" byte > image.jpg

3<#((CUR - 1))



while (( $(3<#) > 0 ))

do

    read -r -u 3 -N 1 byte

    printf "%B" byte >> image.jpg

    3<#((CUR - 2))

done



read -r -u 3 -N 1 byte

printf "%B" byte >> image.jpg



redirect 3<&- || echo 'cannot close FD 3'



exit 0

share|improve this answer

edited Jan 12 '18 at 14:23

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

answered Jan 12 '18 at 14:15

fpmurphyfpmurphy

2,476916

0

I tried the following:

tac -rs '.' input.gnp > output.png

The idea is to force 'tac' using any character as separator.
I tried that on a binary file and it seemed to work but any confirmation would be appreciated.

Main advantage is that it does not load file into memory.

share|improve this answer

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Doesn't work for me (here with GNU tac 8.28) when the input contains newline characters. printf '1n2' | tac -rs . | od -vAn -tc outputs n 2 1 instead of 2 n 1. You'd also need LC_ALL=C or . could match multi-byte characters.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  LC_ALL=C tac -rs $'.\|n' seems to work though.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:25
  

  
  
  
  

add a comment | 

0

I tried the following:

tac -rs '.' input.gnp > output.png

The idea is to force 'tac' using any character as separator.
I tried that on a binary file and it seemed to work but any confirmation would be appreciated.

Main advantage is that it does not load file into memory.

share|improve this answer

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Doesn't work for me (here with GNU tac 8.28) when the input contains newline characters. printf '1n2' | tac -rs . | od -vAn -tc outputs n 2 1 instead of 2 n 1. You'd also need LC_ALL=C or . could match multi-byte characters.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:23
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  LC_ALL=C tac -rs $'.\|n' seems to work though.
  
  – Stéphane Chazelas
  Nov 15 '18 at 20:25
  

  
  
  
  

add a comment | 

I tried the following:

tac -rs '.' input.gnp > output.png

The idea is to force 'tac' using any character as separator.
I tried that on a binary file and it seemed to work but any confirmation would be appreciated.

Main advantage is that it does not load file into memory.

share|improve this answer

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

tac -rs '.' input.gnp > output.png

share|improve this answer

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

answered Apr 16 '18 at 16:00

BouteilleBouteille

1

answered Apr 16 '18 at 16:00

BouteilleBouteille

1