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find - find files
find [-H | -L] path ... [operand_expression ...]
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.
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:
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.
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:
The following primaries shall be supported:
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 .
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.
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.
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.
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.
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 primaries can be combined using the following operators (in order of decreasing precedence):
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.
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.
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.
The following environment variables shall affect the execution of find:
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.
The -print primary shall cause the current pathnames to be written to standard output. The format shall be:
"%s\n", <path>
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.
The following exit values shall be returned:
Default.
The following sections are informative.
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.
The following commands are equivalent:
find . find . -print
They both write out the entire directory hierarchy from the current directory.
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.
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.
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.
The following command:
find . -print -name SCCS -prune
behaves as in the previous example, but prints the names of the SCCS directories.
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
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.
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:
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.)
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.
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()
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