The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


pathchk - check pathnames


pathchk [-p] pathname...


The pathchk utility will check that one or more pathnames are valid (that is, they could be used to access or create a file without causing syntax errors) and portable (that is, no filename truncation will result). More extensive portability checks are provided by the -p option.

By default, the pathchk utility will check each component of each pathname operand based on the underlying file system. A diagnostic will be written for each pathname operand that:

The format of the diagnostic message is not specified, but will indicate the error detected and the corresponding pathname operand.

It will not be considered an error if one or more components of a pathname operand do not exist as long as a file matching the pathname specified by the missing components could be created that does not violate any of the checks specified above.


The pathchk utility supports the XBD specification, Utility Syntax Guidelines  .

The following option is supported:

Instead of performing checks based on the underlying file system, write a diagnostic for each pathname operand that:
  • is longer than {_POSIX_PATH_MAX} bytes (see Minimum Values in the XSH specification <limits.h> description)
  • contains any component longer than {_POSIX_NAME_MAX} bytes
  • contains any character in any component that is not in the portable filename character set.


The following operand is supported:
A pathname to be checked.


Not used.




The following environment variables affect the execution of pathchk:
Provide a default value for the internationalisation variables that are unset or null. If LANG is unset or null, the corresponding value from the implementation-dependent default locale will be used. If any of the internationalisation variables contains an invalid setting, the utility will behave as if none of the variables had been defined.
If set to a non-empty string value, override the values of all the other internationalisation variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single- as opposed to multi-byte characters in arguments).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
Determine the location of message catalogues for the processing of LC_MESSAGES .




Not used.


Used only for diagnostic messages.






The following exit values are returned:
All pathname operands passed all of the checks.
An error occurred.




The test utility can be used to determine if a given pathname names an existing file; it will not, however, give any indication of whether or not any component of the pathname was truncated in a directory where the {_POSIX_NO_TRUNC} feature is not in effect. The pathchk utility does not check for file existence; it performs checks to determine if a pathname does exist or could be created with no pathname component truncation.

The noclobber option in the shell (see the set special built-in) can be used to atomically create a file. As with all file creation semantics in the XSH specification, it guarantees atomic creation, but still depends on applications to agree on conventions and cooperate on the use of files after they have been created.


To verify that all pathnames in an imported data interchange archive are legitimate and unambiguous on the current system:

pax -f archive | sed -e '/ == .*/s///' | xargs pathchk
if [ $? -eq 0 ]
    pax -r -f archive
    echo Investigate problems before importing files.
    exit 1

To verify that all files in the current directory hierarchy could be moved to any system conforming to the XSH specification that also supports the pax utility:

find . -print | xargs pathchk -p
if [ $? -eq 0 ]
    pax -w -f archive .
    echo Portable archive cannot be created.
    exit 1

To verify that a user-supplied pathname names a readable file and that the application can create a file extending the given path without truncation and without overwriting any existing file:

case $- in
    *C*)    reset="";;
    *)      reset="set +C"
            set -C;;
test -r "$path" && pathchk "$path.out" &&
    rm "$path.out" > "$path.out"
if [ $? -ne 0 ]; then
    printf "%s: %s not found or %s.out fails \
creation checks.\n" $0 "$path" "$path"
    $reset    # reset the noclobber option in case a trap
              # on EXIT depends on it
    exit 1
PROCESSING < "$path" > "$path.out"

The following assumptions are made in this example:

  1. PROCESSING represents the code that will be used by the application to use $path once it is verified that $path.out will work as intended.

  2. The state of the noclobber option is unknown when this code is invoked and should be set on exit to the state it was in when this code was invoked. (The reset variable is used in this example to restore the initial state.)

  3. Note the usage of:
    rm "$path.out" > "$path.out"

    1. The pathchk command has already verified, at this point, that $path.out will not be truncated.

    2. With the noclobber option set, the shell will verify that $path.out does not already exist before invoking rm.

    3. If the shell succeeded in creating $path.out, rm will remove it so that the application can create the file again in the PROCESSING step.

    4. If the PROCESSING step wants the file to exist already when it is invoked, the:
      rm "$path.out" > "$path.out"
      should be replaced with:
      > "$path.out"
      which will verify that the file did not already exist, but leave $path.out in place for use by PROCESSING.




test, Redirection .

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Copyright © 1997 The Open Group
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