3.9 Controlling Warning Messages

Sometimes, while performing the requested task, GNU tar notices some conditions that are not exactly errors, but which the user should be aware of. When this happens, tar issues a warning message describing the condition. Warning messages are output to the standard error and they do not affect the exit code of tar command.

GNU tar allows the user to suppress some or all of its warning messages:

--warning=keyword

Control display of the warning messages identified by keyword. If keyword starts with the prefix ‘no-’, such messages are suppressed. Otherwise, they are enabled.

Multiple --warning messages accumulate.

The tables below list allowed values for keyword along with the warning messages they control.

Keywords controlling tar operation

all

Enable all warning messages. This is the default.

none

Disable all warning messages.

filename-with-nuls

‘%s: file name read contains nul character’

alone-zero-block

‘A lone zero block at %s’

Keywords applicable for tar --create

cachedir

‘%s: contains a cache directory tag %s; %s’

file-shrank

‘%s: File shrank by %s bytes; padding with zeros’

xdev

‘%s: file is on a different filesystem; not dumped’

file-ignored

‘%s: Unknown file type; file ignored’
‘%s: socket ignored’
‘%s: door ignored’

file-unchanged

‘%s: file is unchanged; not dumped’

ignore-archive

‘%s: file is the archive; not dumped’

file-removed

‘%s: File removed before we read it’

file-changed

‘%s: file changed as we read it’

Keywords applicable for tar --extract

timestamp

‘%s: implausibly old time stamp %s’
‘%s: time stamp %s is %s s in the future’

contiguous-cast

‘Extracting contiguous files as regular files’

symlink-cast

‘Attempting extraction of symbolic links as hard links’

unknown-cast

‘%s: Unknown file type `%c', extracted as normal file’

ignore-newer

‘Current %s is newer or same age’

unknown-keyword

‘Ignoring unknown extended header keyword `%s'’

decompress-program

Controls verbose description of failures occurring when trying to run alternative decompressor programs (see alternative decompression programs). This warning is disabled by default (unless --verbose is used). A common example of what you can get when using this warning is:

          $ tar --warning=decompress-program -x -f archive.Z
          tar (child): cannot run compress: No such file or directory
          tar (child): trying gzip

This means that tar first tried to decompress archive.Z using compress, and, when that failed, switched to gzip.

Keywords controlling incremental extraction:

rename-directory

‘%s: Directory has been renamed from %s’
‘%s: Directory has been renamed’

new-directory

‘%s: Directory is new’

xdev

‘%s: directory is on a different device: not purging’

bad-dumpdir

‘Malformed dumpdir: 'X' never used’