man/cat1p/pathchk.1p.txt
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pathchk(P) pathchk(P)
NAME pathchk - check pathnames SYNOPSIS pathchk [-p] pathname... DESCRIPTION The pathchk utility shall 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 por- table (that is, no filename truncation results). More extensive portability checks are provided by the -p option. By default, the pathchk utility shall check each compo- nent of each pathname operand based on the underlying file system. A diagnostic shall be written for each pathname operand that: Is longer than {PATH_MAX} bytes (see Pathname Variable Values in the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 13, Headers, <lim- its.h>) 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 shall indicate the error detected and the corre- sponding pathname operand. It shall not be considered an error if one or more com- ponents of a pathname operand do not exist as long as a file matching the pathname specified by the missing com- ponents could be created that does not violate any of the checks specified above. OPTIONS The pathchk utility shall conform to the Base Defini- tions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following option shall be supported: -p Instead of performing checks based on the under- lying file system, write a diagnostic for each pathname operand that: Is longer than {_POSIX_PATH_MAX} bytes (see Mini- mum Values in the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 13, Headers, <lim- its.h>) Contains any component longer than {_POSIX_NAME_MAX} bytes Contains any character in any component that is not in the portable filename character set OPERANDS The following operand shall be supported: pathname A pathname to be checked. STDIN Not used. INPUT FILES None. ENVIRONMENT VARIABLES The following environment variables shall affect the execution of pathchk: LANG Provide a default value for the internationaliza- tion variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale cate- gories.) LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables. LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi- byte characters in arguments). LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic mes- sages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES . ASYNCHRONOUS EVENTS Default. STDOUT Not used. STDERR The standard error shall be used only for diagnostic messages. OUTPUT FILES None. EXTENDED DESCRIPTION None. EXIT STATUS The following exit values shall be returned: 0 All pathname operands passed all of the checks. >0 An error occurred. CONSEQUENCES OF ERRORS Default. The following sections are informative. APPLICATION USAGE The test utility can be used to determine whether a given pathname names an existing file; it does not, how- ever, give any indication of whether or not any compo- nent 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 whether 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 System Inter- faces volume of IEEE Std 1003.1-2001, 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. EXAMPLES To verify that all pathnames in an imported data inter- change archive are legitimate and unambiguous on the current system: pax -f archive | sed -e '/ == .*/s///' | xargs pathchk if [ $? -eq 0 ] then pax -r -f archive else echo Investigate problems before importing files. exit 1 fi To verify that all files in the current directory hier- archy could be moved to any system conforming to the System Interfaces volume of IEEE Std 1003.1-2001 that also supports the pax utility: find . -print | xargs pathchk -p if [ $? -eq 0 ] then pax -w -f archive . else echo Portable archive cannot be created. exit 1 fi To verify that a user-supplied pathname names a readable file and that the application can create a file extend- ing the given path without truncation and without over- writing any existing file: case $- in *C*) reset="";; *) reset="set +C" set -C;; esac test -r "$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 fi $reset PROCESSING < "$path" > "$path.out" The following assumptions are made in this example: PROCESSING represents the code that is used by the application to use $path once it is verified that $path.out works as intended. The state of the noclobber option is unknown when this code is invoked and should be set on exit to the state it was in when this code was invoked. (The reset vari- able is used in this example to restore the initial state.) Note the usage of: rm "$path.out" > "$path.out" <ol type="a"> The pathchk command has already verified, at this point, that $path.out is not truncated. With the noclobber option set, the shell verifies that $path.out does not already exist before invoking rm. If the shell succeeded in creating $path.out, rm removes it so that the application can create the file again in the PROCESSING step. If the PROCESSING step wants the file to exist already when it is invoked, the: rm "$path.out" > "$path.out" should be replaced with: > "$path.out" which verifies that the file did not already exist, but leaves $path.out in place for use by PROCESSING. RATIONALE The pathchk utility was new for the ISO POSIX-2:1993 standard. It, along with the set -C( noclobber) option added to the shell, replaces the mktemp, validfnam, and create utilities that appeared in early proposals. All of these utilities were attempts to solve several common problems: Verify the validity (for several different defi- nitions of "valid") of a pathname supplied by a user, generated by an application, or imported from an external source. Atomically create a file. Perform various string handling functions to gen- erate a temporary filename. The create utility, included in an early proposal, pro- vided checking and atomic creation in a single invocation of the utility; these are orthogonal issues and need not be grouped into a single utility. Note that the noclobber option also provides a way of creating a lock for process synchronization; since it provides an atomic create, there is no race between a test for exis- tence and the following creation if it did not exist. Having a function like tmpnam() in the ISO C standard is important in many high-level languages. The shell pro- gramming language, however, has built-in string manipu- lation facilities, making it very easy to construct tem- porary filenames. The names needed obviously depend on the application, but are frequently of a form similar to: $TMPDIR/application_abbreviation$$.suffix In cases where there is likely to be contention for a given suffix, a simple shell for or while loop can be used with the shell noclobber option to create a file without risk of collisions, as long as applications try- ing to use the same filename name space are cooperating on the use of files after they have been created. FUTURE DIRECTIONS None. SEE ALSO Redirection , set , test COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operat- ing System Interface (POSIX), The Open Group Base Speci- fications Issue 6, Copyright (C) 2001-2003 by the Insti- tute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.open- group.org/unix/online.html . POSIX 2003 pathchk(P) |