man find - Man page for find

June 1, 2007 – 1:41 am

FIND

Section: POSIX Programmer’s Manual (P)
Updated: 2003
Index
Return to Main Contents

---

 

NAME

find – find files
 

SYNOPSIS

find [–H | –L] path … [operand_expression
...]
 

DESCRIPTION

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.

Specifying more than one of the mutually–exclusive options –H
and –L shall not be considered an error. The last
option specified shall determine the behavior of the utility.
 

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.

The following primaries shall be supported:

–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.

If the hyphen is omitted, the primary shall evaluate as true when
the file permission bits exactly match the value of the
resulting template.

Otherwise, if mode is prefixed by a hyphen, the primary shall
evaluate as true if at least all the bits in the resulting
template are set in the file permission bits.

–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.

If the primary expression is punctuated by a semicolon, the utility
utility_name shall be invoked once for each pathname
and the primary shall evaluate as true if the utility returns a zero
value as exit status. A utility_name or argument
containing only the two characters "{}" shall be replaced by
the current pathname.

If the primary expression is punctuated by a plus sign, the primary
shall always evaluate as true, and the pathnames for which
the primary is evaluated shall be aggregated into sets. The utility
utility_name shall be invoked once for each set of
aggregated pathnames. Each invocation shall begin after the last pathname
in the set is aggregated, and shall be completed before
the find utility exits and before the first pathname in the
next set (if any) is aggregated for this primary, but it is
otherwise unspecified whether the invocation occurs before, during,
or after the evaluations of other primaries. If any invocation
returns a non–zero value as exit status, the find utility shall
return a non–zero exit status. An argument containing only
the two characters "{}" shall be replaced by the set of aggregated
pathnames, with each pathname passed as a separate
argument to the invoked utility in the same order that it was aggregated.
The size of any set of two or more pathnames shall be
limited such that execution of the utility does not cause the system’s
{ARG_MAX} limit to be exceeded. If more than one argument
containing only the two characters "{}" is present, the behavior
is unspecified.

If a utility_name or argument string contains the two
characters "{}" , but not just the two characters
"{}" , it is implementation–defined whether find replaces
those two characters or uses the string without change.
The current directory for the invocation of utility_name shall
be the same as the current directory when the find
utility was started. If the utility_name names any of the special
built–in utilities (see Special Built–In Utilities ), the results
are undefined.

–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.

–print

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.

The primaries can be combined using the following operators (in order
of decreasing precedence):

( 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.

If no expression is present, –print shall be used as the
expression. Otherwise, if the given expression does not
contain any of the primaries –exec, –ok, or –print,
the given expression shall be effectively replaced by:

( given_expression ) –print

The –user, –group, and –newer primaries each shall
evaluate their respective arguments only once.
 

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.
 

EXAMPLES

1.

The following commands are equivalent:

find .

find . –print

They both write out the entire directory hierarchy from the current
directory.

2.

The following command:

find / \( –name tmp –o –name ‘*.xx’ \) –atime +7 –exec rm {} \;

removes all files named tmp or ending in .xx that have
not been accessed for seven or more 24–hour periods.

3.

The following command:

find . –perm –o+w,+s

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.

4.

The following command:

find . –name SCCS –prune –o –print

recursively prints pathnames of all files in the current directory
and below, but skips directories named SCCS and files in
them.

5.

The following command:

find . –print –name SCCS –prune

behaves as in the previous example, but prints the names of the SCCS
directories.

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

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.

 

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.

Therefore, an application using this prompting option relies on the
system to provide the most suitable dialog directly with the
user, based on the general guidelines specified.

The –name file operand was changed to use the shell pattern
matching notation so that find is consistent
with other utilities using pattern matching.

The –size operand refers to the size of a file, rather than
the number of blocks it may occupy in the file system. The
intent is that the st_size field defined in the System Interfaces
volume of IEEE Std 1003.1–2001 should be used,
not the st_blocks found in historical implementations. There
are at least two reasons for this:

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.)

The descriptions of –atime, –ctime, and –mtime were
changed from the SVID description of n "days”
to "24–hour periods". The description is also different in terms of
the exact timeframe for the n case (versus the
+n or –n), but it matches all known historical implementations.
It refers to one 86400 second period in the past, not
any time from the beginning of that period to the current time. For
example, –atime 3 is true if the file was accessed any
time in the period from 72 hours to 48 hours ago.

Historical implementations do not modify "{}" when it appears
as a substring of an –exec or –ok
utility_name or argument string. There have been numerous user
requests for this extension, so this volume of
IEEE Std 1003.1–2001 allows the desired behavior. At least one recent
implementation does support this feature, but
encountered several problems in managing memory allocation and dealing
with multiple occurrences of "{}" in a string while
it was being developed, so it is not yet required behavior.

Assuming the presence of –print was added to correct a historical
pitfall that plagues novice users, it is entirely
upwards–compatible from the historical System V find utility.
In its simplest form ( find directory), it could
be confused with the historical BSD fast find. The BSD developers
agreed that adding –print as a default expression
was the correct decision and have added the fast find functionality
within a new utility called locate.

Historically, the –L option was implemented using the primary
–follow. The –H and –L options were
added for two reasons. First, they offer a finer granularity of control
and consistency with other programs that walk file
hierarchies. Second, the –follow primary always evaluated to
true. As they were historically really global variables that
took effect before the traversal began, some valid expressions had
unexpected results. An example is the expression –print
–o –follow. Because –print always evaluates to true,
the standard order of evaluation implies that
–follow would never be evaluated. This was never the case. Historical
practice for the –follow primary, however, is
not consistent. Some implementations always follow symbolic links
on the command line whether –follow is specified or not.
Others follow symbolic links on the command line only if –follow
is specified. Both behaviors are provided by the –H
and –L options, but scripts using the current –follow
primary would be broken if the –follow option is
specified to work either way.

Since the –L option resolves all symbolic links and the –type
l primary is true for symbolic links that
still exist after symbolic links have been resolved, the command:

find –L . –type l

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:

find / –type f –exec echo {} – ‘;’ –o –exec echo {} + ‘;’

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.
 

FUTURE DIRECTIONS

None.
 

SEE ALSO

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 .

---

 

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

OPERANDS

STDIN

INPUT FILES

ENVIRONMENT VARIABLES

ASYNCHRONOUS EVENTS

STDOUT

STDERR

OUTPUT FILES

EXTENDED DESCRIPTION

EXIT STATUS

CONSEQUENCES OF ERRORS

APPLICATION USAGE

EXAMPLES

RATIONALE

FUTURE DIRECTIONS

SEE ALSO

COPYRIGHT

---