Using sed to mass rename files

Question

Objective  Change these filenames    F00001-0708-RG-biasliuyda F00001-0708-CS-akgdlaul F00001-0708-VF-hioulgigl   to these filenames    F0001-0708-RG-biasliuyda F0001-0708-CS-akgdlaul F0001-0708-VF-hioulgigl   Shell Code  To test   ls F00001-0708-  sed  s              mv  amp   1 2     To perform   ls F00001-0708-  sed  s              mv  amp   1 2     sh   My Question  I don t understand the sed code   I understand what the substitution command    sed  s something mv    means   And I understand regular expressions somewhat   But I don t understand what s happening here                  or here    amp   1 2    The former  to me  just looks like it means   a single character  followed by a single character  followed by any length sequence of a single character --but surely there s more to it than that   As far as the latter part    amp   1 2    I have no idea

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If all you re really doing is removing the second character  regardless of what it is  you can do this   s    2   but your command is building a mv command and piping it to the shell for execution   This is no more readable than your version   find -type f   sed -n  h s    4 x s   mv   G s  n   g p    sh   The fourth character is removed because find is prepending each filename with

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The easiest way would be   for i in F00001   do mv   i     i F00001 F0001    done   or  portably   for i in F00001   do mv   i   F0001  i F00001    done   This replaces the F00001 prefix in the filenames with F0001  credits to mahesh here  http   www debian-administration org articles 150

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First  I should say that the easiest way to do this is to use the prename or rename commands   On Ubuntu  OSX  Homebrew package rename  MacPorts package p5-file-rename   or other systems with perl rename  prename    rename s 0000 000  F0000    or on systems with rename from util-linux-ng  such as RHEL   rename 0000 000 F0000    That s a lot more understandable than the equivalent sed command   But as for understanding the sed command  the sed manpage is helpful  If you run man sed and search for  amp   using the   command to search   you ll find it s a special character in s foo bar  replacements     s regexp replacement           Attempt  to match regexp against the pattern space   If success-          ful   replace  that  portion  matched  with  replacement     The          replacement may contain the special character  amp  to refer to that          portion of the pattern space  which  matched   and  the  special          escapes   1  through   9  to refer to the corresponding matching          sub-expressions in the regexp    Therefore        matches the first character  which can be referenced by  1  Then   matches the next character  which is always 0  Then        matches the rest of the filename  which can be referenced by  2   The replacement string puts it all together using  amp   the original filename  and  1 2 which is every part of the filename except the 2nd character  which was a 0   This is a pretty cryptic way to do this  IMHO   If for some reason the rename command was not available and you wanted to use sed to do the rename  or perhaps you were doing something too complex for rename    being more explicit in your regex would make it much more readable   Perhaps something like   ls F00001-0708-  sed  s F0000       mv  amp  F000 1     sh   Being able to see what s actually changing in the s search replacement  makes it much more readable  Also it won t keep sucking characters out of your filename if you accidentally run it twice or something

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Here s what I would do   for file in    Jj  Pp  Gg   do      echo mv -vi    file    jhead  file                             grep Date                             cut -b 16-                             sed -e  s   - g  -e  s     g  -e  s    jpg g     done   Then if that looks ok  add   sh to the end  So   for file in    Jj  Pp  Gg   do      echo mv -vi    file    jhead  file                             grep Date                             cut -b 16-                             sed -e  s   - g  -e  s     g  -e  s    jpg g     done   sh

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The sed command  s              mv  amp   1 2    means to replace                  with   mv  amp   1 2   just like a regular sed command  However  the parentheses   amp  and  n markers change it a little   The search string matches  and remembers as pattern 1  the single character at the start  followed by a single character  follwed by the rest of the string  remembered as pattern 2    In the replacement string  you can refer to these matched patterns to use them as part of the replacement  You can also refer to the whole matched portion as  amp    So what that sed command is doing is creating a mv command based on the original file  for the source  and character 1 and 3 onwards  effectively removing character 2  for the destination   It will give you a series of lines along the following format   mv F00001-0708-RG-biasliuyda F0001-0708-RG-biasliuyda mv abcdef acdef   and so on

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for i in    do mv  i   echo  i sed  s AAA BBB     done

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The parentheses capture particular strings for use by the backslashed numbers

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The backslash-paren stuff means   while matching the pattern  hold on to the stuff that matches in here    Later  on the replacement text side  you can get those remembered fragments back with   1   first parenthesized block     2   second block   and so on

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Using perl rename  a must have in the toolbox   rename -n  s 0000 000   F0000   Remove -n switch when the output looks good to rename for real   There are other tools with the same name which may or may not be able to do this  so be careful   The rename command that is part of the util-linux package  won t  If you run the following command  GNU    rename  and you see perlexpr  then this seems to be the right tool  If not  to make it the default  usually already the case  on Debian and derivative like Ubuntu     sudo apt install rename   sudo update-alternatives --set rename  usr bin file-rename   For archlinux  pacman -S perl-rename   For RedHat-family distros  yum install prename  The  prename  package is in the EPEL repository   For Gentoo  emerge dev-perl rename   For  BSD  pkg install gprename  or p5-File-Rename  For Mac users  brew install rename   If you don t have this command with another distro  search your package manager to install it or do it manually  cpan -i File  Rename  Old standalone version can be found here  man rename  This tool was originally written by Larry Wall  the Perl s dad

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I wrote a small post with examples on batch renaming using sed couple of years ago   http   www guyrutenberg com 2009 01 12 batch-renaming-using-sed   For example   for i in    do   mv   i    echo  i   sed  s regex replace text      done   If the regex contains groups  e g    subregex   then you can use them in the replacement text as  1   2 etc

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Some examples that work for me    tree -L 1 -F      -- A Show 2020 1400MB txt  -- Some Show S01E01 the Loreming txt  0 directories  2 files     remove  quot 1400MB quot   I  ignore case         for f in    do mv 2 gt  dev null -v  quot  f quot   quot  echo  f   sed -r  s   0-9  1  mb  I   quot   done  renamed  A Show 2020 1400MB txt  - gt   A Show 2020 txt      change  quot S01E01 the quot  to  quot S01E01 The quot      U amp    change  here  regex-selected  text to uppercase           note also  no need here for   1  in that regex expression    for f in    do mv 2 gt  dev null  quot  f quot   quot  echo  f   sed -r  quot s   0-9   a-z    U amp   quot   quot   done    tree -L 1 -F      -- A Show 2020 txt  -- Some Show S01E01 The Loreming txt  0 directories  2 files      2 gt  dev null suppresses extraneous output  warnings       reference  this thread   https   stackoverflow com a 2372808 1904943  change case  https   www networkworld com article 3529409 converting-between-uppercase-and-lowercase-on-the-linux-command-line html

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you ve had your sed explanation  now you can use just the shell  no need external commands   for file in F0000  do     echo mv   file     file  F0000 F000           file  F0000 F000  means replace the pattern that starts at beginning of string done

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ls F00001-0708-  sed  s  F0000       mv  amp  F000 1     bash

[bash] Using sed to mass rename files

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