[Linux manuál]
Návod, kniha: POSIX Programmer's Manual
The -user, -group, and -newer primaries each shall evaluate
their respective arguments only once.
They both write out the entire directory hierarchy from the current directory.
removes all files named tmp or ending in .xx that have not been
accessed for seven or more 24-hour periods.
prints ( -print is assumed) the names of all files in or below the
current directory, with all of the file permission bits S_ISUID, S_ISGID, and
S_IWOTH set.
recursively prints pathnames of all files in the current directory and below,
but skips directories named SCCS and files in them.
behaves as in the previous example, but prints the names of the SCCS
directories.
at 00:01 the next day (less than 24 hours later, not more than one day ago); the
midnight boundary between days has no effect on the 24-hour calculation.
prints a list of symbolic links reachable from the current directory that do not
resolve to accessible files.
A feature of SVR4's find utility was the -exec primary's +
terminator. This allowed filenames containing special characters (especially
<newline>s) to be grouped together without the problems that occur if
such filenames are piped to xargs. Other implementations have added
other ways to get around this problem, notably a -print0 primary that
wrote filenames with a null byte terminator. This was considered here, but not
adopted. Using a null terminator meant that any utility that was going to
process find's -print0 output had to add a new option to parse
the null terminators it would now be reading.
The "-exec ... {} +" syntax adopted was a result of IEEE PASC
Interpretation 1003.2 #210. It should be noted that this is an incompatible
change to the ISO/IEC 9899:1999 standard. For example, the following
command prints all files with a '-' after their name if they are
regular files, and a '+' otherwise:
The change invalidates usage like this. Even though the previous standard stated
that this usage would work, in practice many did not support it and the
standard developers felt it better to now state that this was not allowable.
find: najít soubory
Originální popis anglicky: find - find filesNávod, kniha: POSIX Programmer's Manual
STRUČNĚ
find [-H | -L] path ... [operand_expression ...]POPIS / INSTRUKCE
The find utility shall recursively descend the directory hierarchy from each file specified by path, evaluating a Boolean expression composed of the primaries described in the OPERANDS section for each file encountered. The find utility shall be able to descend to arbitrary depths in a file hierarchy and shall not fail due to path length limitations (unless a path operand specified by the application exceeds {PATH_MAX} requirements). The find utility shall detect infinite loops; that is, entering a previously visited directory that is an ancestor of the last file encountered. When it detects an infinite loop, find shall write a diagnostic message to standard error and shall either recover its position in the hierarchy or terminate.OPTIONS
The find utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following options shall be supported by the implementation:- -H
- Cause the file information and file type evaluated for each symbolic link encountered on the command line to be those of the file referenced by the link, and not the link itself. If the referenced file does not exist, the file information and type shall be for the link itself. File information for all symbolic links not on the command line shall be that of the link itself.
- -L
- Cause the file information and file type evaluated for each
symbolic link to be those of the file referenced by the link, and not the
link itself.
OPERANDS
The following operands shall be supported: The path operand is a pathname of a starting point in the directory hierarchy. The first argument that starts with a '-' , or is a '!' or a '(' , and all subsequent arguments shall be interpreted as an expression made up of the following primaries and operators. In the descriptions, wherever n is used as a primary argument, it shall be interpreted as a decimal integer optionally preceded by a plus ( '+' ) or minus ( '-' ) sign, as follows:- +n
- More than n.
- n
- Exactly n.
- -n
- Less than n.
- -name pattern
-
The primary shall evaluate as true if the basename of the filename being examined matches pattern using the pattern matching notation described in Pattern Matching Notation .
- -nouser
- The primary shall evaluate as true if the file belongs to a user ID for which the getpwuid() function defined in the System Interfaces volume of IEEE Std 1003.1-2001 (or equivalent) returns NULL.
- -nogroup
- The primary shall evaluate as true if the file belongs to a group ID for which the getgrgid() function defined in the System Interfaces volume of IEEE Std 1003.1-2001 (or equivalent) returns NULL.
- -xdev
- The primary shall always evaluate as true; it shall cause find not to continue descending past directories that have a different device ID ( st_dev, see the stat() function defined in the System Interfaces volume of IEEE Std 1003.1-2001). If any -xdev primary is specified, it shall apply to the entire expression even if the -xdev primary would not normally be evaluated.
- -prune
- The primary shall always evaluate as true; it shall cause find not to descend the current pathname if it is a directory. If the -depth primary is specified, the -prune primary shall have no effect.
- -perm [-]mode
-
The mode argument is used to represent file mode bits. It shall be identical in format to the symbolic_mode operand described in chmod() , and shall be interpreted as follows. To start, a template shall be assumed with all file mode bits cleared. An op symbol of '+' shall set the appropriate mode bits in the template; '-' shall clear the appropriate bits; '=' shall set the appropriate mode bits, without regard to the contents of process' file mode creation mask. The op symbol of '-' cannot be the first character of mode; this avoids ambiguity with the optional leading hyphen. Since the initial mode is all bits off, there are not any symbolic modes that need to use '-' as the first character.
- -perm [-]onum
-
If the hyphen is omitted, the primary shall evaluate as true when the file permission bits exactly match the value of the octal number onum and only the bits corresponding to the octal mask 07777 shall be compared. (See the description of the octal mode in chmod() .) Otherwise, if onum is prefixed by a hyphen, the primary shall evaluate as true if at least all of the bits specified in onum that are also set in the octal mask 07777 are set.
- -type c
- The primary shall evaluate as true if the type of the file is c, where c is 'b' , 'c' , 'd' , 'l' , 'p' , 'f' , or 's' for block special file, character special file, directory, symbolic link, FIFO, regular file, or socket, respectively.
- -links n
- The primary shall evaluate as true if the file has n links.
- -user uname
- The primary shall evaluate as true if the file belongs to the user uname. If uname is a decimal integer and the getpwnam() (or equivalent) function does not return a valid user name, uname shall be interpreted as a user ID.
- -group gname
-
The primary shall evaluate as true if the file belongs to the group gname. If gname is a decimal integer and the getgrnam() (or equivalent) function does not return a valid group name, gname shall be interpreted as a group ID.
- -size n[c]
- The primary shall evaluate as true if the file size in bytes, divided by 512 and rounded up to the next integer, is n. If n is followed by the character 'c' , the size shall be in bytes.
- -atime n
- The primary shall evaluate as true if the file access time subtracted from the initialization time, divided by 86400 (with any remainder discarded), is n.
- -ctime n
- The primary shall evaluate as true if the time of last change of file status information subtracted from the initialization time, divided by 86400 (with any remainder discarded), is n.
- -mtime n
- The primary shall evaluate as true if the file modification time subtracted from the initialization time, divided by 86400 (with any remainder discarded), is n.
- -exec utility_name [argument ...] ;
- -exec utility_name [argument ...]
- {} +
The end of the primary expression shall be punctuated by a semicolon or by a plus sign. Only a plus sign that follows an argument containing the two characters "{}" shall punctuate the end of the primary expression. Other uses of the plus sign shall not be treated as special.
- -ok utility_name [argument ... ] ;
-
The -ok primary shall be equivalent to -exec, except that the use of a plus sign to punctuate the end of the primary expression need not be supported, and find shall request affirmation of the invocation of utility_name using the current file as an argument by writing to standard error as described in the STDERR section. If the response on standard input is affirmative, the utility shall be invoked. Otherwise, the command shall not be invoked and the value of the -ok operand shall be false.
- The primary shall always evaluate as true; it shall cause the current pathname to be written to standard output.
- -newer file
- The primary shall evaluate as true if the modification time of the current file is more recent than the modification time of the file named by the pathname file.
- -depth
- The primary shall always evaluate as true; it shall cause
descent of the directory hierarchy to be done so that all entries in a
directory are acted on before the directory itself. If a -depth
primary is not specified, all entries in a directory shall be acted on
after the directory itself. If any -depth primary is specified, it
shall apply to the entire expression even if the -depth primary
would not normally be evaluated.
- ( expression )
- True if expression is true.
- ! expression
- Negation of a primary; the unary NOT operator.
- expression [-a] expression
-
Conjunction of primaries; the AND operator is implied by the juxtaposition of two primaries or made explicit by the optional -a operator. The second expression shall not be evaluated if the first expression is false.
- expression -o expression
-
Alternation of primaries; the OR operator. The second expression shall not be evaluated if the first expression is true.
( given_expression ) -print
STDIN
If the -ok primary is used, the response shall be read from the standard input. An entire line shall be read as the response. Otherwise, the standard input shall not be used.INPUT FILES
None.ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of find:- LANG
- Provide a default value for the internationalization 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 categories.)
- LC_ALL
- If set to a non-empty string value, override the values of all the other internationalization variables.
- LC_COLLATE
-
Determine the locale for the behavior of ranges, equivalence classes, and multi-character collating elements used in the pattern matching notation for the -n option and in the extended regular expression defined for the yesexpr locale keyword in the LC_MESSAGES category.
- LC_CTYPE
- This variable determines 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), the behavior of character classes within the pattern matching notation used for the -n option, and the behavior of character classes within regular expressions used in the extended regular expression defined for the yesexpr locale keyword in the LC_MESSAGES category.
- LC_MESSAGES
- Determine the locale for the processing of affirmative responses that should be used to affect the format and contents of diagnostic messages written to standard error.
- NLSPATH
- Determine the location of message catalogs for the processing of LC_MESSAGES .
- PATH
- Determine the location of the utility_name for the
-exec and -ok primaries, as described in the Base
Definitions volume of IEEE Std 1003.1-2001, Chapter 8,
Environment Variables.
ASYNCHRONOUS EVENTS
Default.STDOUT
The -print primary shall cause the current pathnames to be written to standard output. The format shall be:"%s\n", <path>
STDERR
The -ok primary shall write a prompt to standard error containing at least the utility_name to be invoked and the current pathname. In the POSIX locale, the last non- <blank> in the prompt shall be '?' . The exact format used is unspecified. Otherwise, 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 path operands were traversed successfully.
- >0
- An error occurred.
CONSEQUENCES OF ERRORS
Default. The following sections are informative.APPLICATION USAGE
When used in operands, pattern matching notation, semicolons, opening parentheses, and closing parentheses are special to the shell and must be quoted (see Quoting ). The bit that is traditionally used for sticky (historically 01000) is specified in the -perm primary using the octal number argument form. Since this bit is not defined by this volume of IEEE Std 1003.1-2001, applications must not assume that it actually refers to the traditional sticky bit.PŘÍKLADY POUŽITÍ
- 1.
- The following commands are equivalent:
find . find . -print
- 2.
- The following command:
find / \( -name tmp -o -name '*.xx' \) -atime +7 -exec rm {} \;
- 3.
- The following command:
find . -perm -o+w,+s
- 4.
- The following command:
find . -name SCCS -prune -o -print
- 5.
- The following command:
find . -print -name SCCS -prune
- 6.
- The following command is roughly equivalent to the
-nt extension to test:
if [ -n "$(find file1 -prune -newer file2)" ]; then
printf %s\\n "file1 is newer than file2"
fi
- 7.
- The descriptions of -atime, -ctime, and
-mtime use the terminology n "86400 second periods
(days)". For example, a file accessed at 23:59 is selected by:
find . -atime -1 -print
RATIONALE
The -a operator was retained as an optional operator for compatibility with historical shell scripts, even though it is redundant with expression concatenation. The descriptions of the '-' modifier on the mode and onum arguments to the -perm primary agree with historical practice on BSD and System V implementations. System V and BSD documentation both describe it in terms of checking additional bits; in fact, it uses the same bits, but checks for having at least all of the matching bits set instead of having exactly the matching bits set. The exact format of the interactive prompts is unspecified. Only the general nature of the contents of prompts are specified because:- *
- Implementations may desire more descriptive prompts than those used on historical implementations.
- *
- Since the historical prompt strings do not terminate with <newline>s, there is no portable way for another program to interact with the prompts of this utility via pipes.
- 1.
- In both System V and BSD, find only uses st_size in size calculations for the operands specified by this volume of IEEE Std 1003.1-2001. (BSD uses st_blocks only when processing the -ls primary.)
- 2.
- Users usually think of file size in terms of bytes, which is also the unit used by the ls utility for the output from the -l option. (In both System V and BSD, ls uses st_size for the -l option size field and uses st_blocks for the ls -s calculations. This volume of IEEE Std 1003.1-2001 does not specify ls -s.)
find -L . -type l
find / -type f -exec echo {} - ';' -o -exec echo {} + ';'
FUTURE DIRECTIONS
None.SOUVISEJÍCÍ
Quoting , Pattern Matching Notation , Special Built-In Utilities , chmod() , pax , sh , test , the System Interfaces volume of IEEE Std 1003.1-2001, getgrgid(), getpwuid(), stat()COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute 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.opengroup.org/unix/online.html .| 2003 | IEEE/The Open Group |