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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022



pathchk - check path names


pathchk [-p] path...


The pathchk command will check that one or more path names 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, pathchk will check each component of each path operand based on the underlying file system. A diagnostic will be written for each path operand that:

  • is longer than PATH_MAX bytes.

  • contains any component longer than NAME_MAX bytes in its containing directory

  • contains any component in a directory that is not searchable

  • contains any character in any component that is not valid in its containing directory.

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

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


The following option is supported:


Instead of performing checks based on the underlying file system, write a diagnostic for each path operand that:

  • is longer than _POSIX_PATH_MAX bytes

  • contains any component longer than _POSIX_NAME_MAX bytes

  • contains any character in any component that is not in the portable filename character set.


Prints an error message if a file name is empty, or if it contains a component that begins with an '-' (hyphen).


The following operand is supported:


A path to be checked.


Example 1 Using the pathchk command

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

example% 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 X/Open specification that also supports the pax(1) command:

example% 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 path names a readable file and that the application can create a file extending the given path without truncation and without overwriting any existing file:

example% 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"

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


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


    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.


    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.

Environment Variables

See environ(7) for descriptions of the following environment variables that affect the execution of pathchk: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:


All path operands passed all of the checks.


An error occurred.


See attributes(7) for descriptions of the following attributes:

Interface Stability

See Also

pax(1), test(1), attributes(7), environ(7), standards(7)