tar file changed as we read it

Question

I am using make and tar to backup  When executing makefile  tar command shows file changed as we read it  In this case    the tar package is ok when the warning comes up but it stops the tar command for the following backup the file showing the warning in fact doesn t change -- it is really strange that the warning comes up the files showing the warning come up randomly  I mean  everytime I run my makefile  the files showing the warning are different --ignore-failed-read doesn t help  I am using tar 1 23 in MinGW I just changed my computer to WIN7 64 bit  The script works well in old WIN7 32 bit  But the tar version is not as new as the 1 23    How can I stop the tar s warning to stop my backup following the warning     Edit-2  it might be the reason  As I said above  the bash shell script worked well in my old computer  Comparing with the old computer  the msys version is different  So is the version of tar command  In the old computer  tar is 1 13 19 and it is 1 23 in the new computer  I copied the old tar command without copying its dependency msys-1 0 dll to the new computer and renamed it tar old  And I also updated the tar command in the shell script and run the script  Then everything is ok  So  it seemed that the problem is the tar command  I am sure that there is no any file changed when taring  Is it a bug for tar command in new version  I don t know     Edit-1  add more details  The backup is invoked by a bash shell script  It scans the target directory and builds makefile then invokes make to use tar command for backup  Followed is a typical makefile built by the bash shell script    --------------------------------------------   backup VC  --------------------------------------------   the program for packing PACK TOOL tar    the option for packing tool PACK OPTION cjvf    M   C driver WIN C DIR c     M   D driver WIN D DIR d     M   where the software is WIN PRG DIR wuyu tools   WIN PRG DIR     where to save the backup files BAKDIR  home Wu Y MS bak MSYS  VC FRAMEWORK  home Wu Y MS bak MSYS tools VC VC framework tar bz2 VC 2010  home Wu Y MS bak MSYS tools VC VC 2010 tar bz2   PHONY  all  all    VC FRAMEWORK    VC 2010     VC FRAMEWORK     WIN C DIR    WIN PRG DIR  VC Framework          PACK TOOL    PACK OPTION       --ignore-failed-read  c   WIN PRG DIR  VC Framework   VC 2010     WIN C DIR    WIN PRG DIR  VC VS2010          PACK TOOL    PACK OPTION       --ignore-failed-read  c   WIN PRG DIR  VC VS2010   As you can see  the tar package is stored in   MS bak MSYS tools VC VC 2010 tar bz2  I run the script in   qqaa    MS bak MSYS is excluded from tar command  So  the tar file I am creating is not inside a directory I am trying to put into tar file  This is why I felt it strange that the warning came up

User · Answer

Although its very late but I recently had the same issue.

Issue is because dir . is changing as xyz.tar.gz is created after running the command. There are two solutions:

Solution 1: tar will not mind if the archive is created in any directory inside .. There can be reasons why can't create the archive outside the work space. Worked around it by creating a temporary directory for putting the archive as:

mkdir artefacts
tar -zcvf artefacts/archive.tar.gz --exclude=./artefacts .
echo $?
0

Solution 2: This one I like. create the archive file before running tar:

touch archive.tar.gz
tar --exclude=archive.tar.gz -zcvf archive.tar.gz .
echo $?
0

User · Answer

To enhance Fabian s one-liner  let us say that we want to ignore only exit status 1 but to preserve the exit status if it is anything else   tar -czf sample tar gz dir1 dir2      export ret         ret -eq 1       exit   ret      This does everything sandeep s script does  on one line

User · Answer

Here is a one-liner for ignoring the tar exit status if it is 1  There is no need to set  e as in sandeep s script  If the tar exit status is 0 or 1  this one-liner will return with exit status 0  Otherwise it will return with exit status 1  This is different from sandeep s script where the original exit status value is preserved if it is different from 1   tar -czf sample tar gz dir1 dir2          -eq 1

User · Answer

I also encounter the tar messages  changed as we read it   For me these message occurred when I was making tar file of Linux file system in bitbake build environment  This error was sporadic   For me this was not due to creating tar file from the same directory  I am assuming there is actually some file overwritten or changed during tar file creation   The message is a warning and it still creates the tar file  We can still suppress these warning message by setting option   --warning no-file-changed   http   www gnu org software tar manual html section warnings html     Still the exit code return by the tar is  1  in warning message case  http   www gnu org software tar manual html section Synopsis html  So if we are calling the tar file from some function in scripts  we can handle the exit code something like this   set  e  tar -czf sample tar gz dir1 dir2 exitcode     if     exitcode      1     amp  amp      exitcode      0     then     exit  exitcode fi set -e

User · Answer

I am not sure does it suit you but I noticed that tar does not fail on changed deleted files in pipe mode  See what I mean   Test script      usr bin env bash set -ex tar cpf -   files   aws s3 cp - s3   my-bucket files tar echo      Deleting random files manually     Output     aws s3 cp - s3   my-bucket files tar   tar cpf -   files tar    files default images  File removed before we read it tar    files  file changed as we read it   echo 0 0

User · Answer

If you want help debugging a problem like this you need to provide the make rule or at least the tar command you invoked   How can we see what s wrong with the command if there s no command to see   However  99  of the time an error like this means that you re creating the tar file inside a directory that you re trying to put into the tar file   So  when tar tries to read the directory it finds the tar file as a member of the directory  starts to read it and write it out to the tar file  and so between the time it starts to read the tar file and when it finishes reading the tar file  the tar file has changed   So for example something like   tar cf   foo tar     There s no way to  stop  this  because it s not wrong   Just put your tar file somewhere else when you create it  or find another way  using --exclude or whatever  to omit the tar file

User · Answer

Simply using an outer directory for the output  solved the problem for me   sudo tar czf      31OCT18 tar gz

User · Answer

It worked for me by adding a simple sleep timeout of 20 sec  This might happen if your source directory is still writing  Hence put a sleep so that the backup would finish and then tar should work fine  This also helped me in getting the right exit status   sleep 20 tar -czf   DB    DATE  tgz     DB    DATE

[makefile] tar: file changed as we read it

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