neulab/tldr huggingface dataset:
The maintainer of CopyQ is Lukas Holecek <hluk@email.cz>. A comprehensive list of authors and contributors is available in the AUTHORS file.
This manual page was written by GengYu Rao (zouyoo@outlook.com), for the Debian project (and may be used by others).
SHARDS(1)                         Shards Manual                        SHARDS(1)
shards - dependency manager for the Crystal Language
shards [<general_options>...] [<command>] [<command_options>...]
Manages dependencies for Crystal projects and libraries with reproducible installs across computers and systems.
shards requires the presence of a shard.yml file in the project folder (working directory). This file describes the project and lists dependencies that are required to build it. See shard.yml(5) for more information on its format. A default file can be created by running shards init.
Running shards install resolves and installs the specified dependencies. The installed versions are written into a shard.lock file for using the exact same dependency versions when running shards install again.
If your shard builds an application, both shard.yml and shard.lock should be checked into version control to provide reproducible dependency installs. If it is only a library for other shards to depend on, shard.lock should not be checked in, only shard.yml. It’s good advice to add it to .gitignore.
If no command is given, install command will be run by default.
To see the available options for a particular command, use --help after the command.
build [<targets>] [<build_options>...] Builds the specified <targets> in bin path. If no targets are specified, all are built. This command ensures all dependencies are installed, so it is not necessary to run shards install before.
All <build_options> following the command are delegated to crystal build.
check Verifies that all dependencies are installed and requirements are satisfied.
Exit status:
0 Dependencies are satisfied.
1 Dependencies are not satisfied.
init Initializes a default shard.yml in the current folder.
install [--frozen] [--without-development] [--production] [--skip-postinstall] [--skip-executables] Resolves and installs dependencies into the lib folder. If not already present, generates a shard.lock file from resolved dependencies, locking version numbers or Git commits.
Reads and enforces locked versions and commits if a shard.lock file is present. The install command may fail if a locked version doesn’t match a requirement, but may succeed if a new dependency was added, as long as it doesn’t generate a conflict, thus generating a new shard.lock file.
--frozen Strictly installs locked versions from shard.lock. Fails if shard.lock is missing.
--without-development Does not install development dependencies.
--production same as --frozen and --without-development
--skip-postinstall Does not run postinstall of dependencies.
--skip-executables Does not install executables.
list [--tree] Lists the installed dependencies and their versions.
Specifying --tree arranges nested dependencies in a tree, instead of a flattened list.
lock [--update [<shards>...]] Resolves dependencies and creates or updates the shard.lock file as per the install command, but never installs the dependencies.
Specifying --update follows the same semantics as the update command.
outdated [--pre] Lists dependencies that are outdated.
When --pre is specified, pre-release versions are also considered.
prune Removes unused dependencies from lib folder.
update [<shards>...] Resolves and updates all dependencies into the lib folder, whatever the locked versions in the shard.lock file. Eventually generates a new shard.lock file.
Specifying shards will update these dependencies only, trying to be as conservative as possible with other dependencies, respecting the locked versions in the shard.lock file.
version [<path>] Prints the current version of the shard located at path (defaults to current directory).
To see the available options for a particular command, use --help after a command.
--version Prints the version of shards.
-h, --help Prints usage synopsis.
--no-color Disables colored output.
--local Don’t update remote repositories, use the local cache only.
-q, --quiet Decreases the log verbosity, printing only warnings and errors.
-v, --verbose Increases the log verbosity, printing all debug statements.
Shards is usually distributed with Crystal itself. Alternatively, a separate shards package may be available for your system.
To install from source, download or clone the repository <https://github.com/crystal-lang/shards> and run make CRFLAGS=--release. The compiled binary is in bin/shards and should be added to PATH.
SHARDS_OPTS Allows general options to be passed in as environment variable. Example: SHARDS_OPTS="--no-color" shards update
SHARDS_CACHE_PATH Defines the cache location. In this folder, shards stores local copies of remote repositories. Defaults to .cache/shards in the home directory ($XDG_CACHE_HOME or $HOME) or the current directory.
SHARDS_INSTALL_PATH Defines the location where dependecies are installed. Defaults to lib.
SHARDS_BIN_PATH Defines the location where executables are installed. Defaults to bin.
CRYSTAL_VERSION Defines the crystal version that dependencies should be resolved against. Defaults to the output of crystal env CRYSTAL_VERSION.
SHARDS_OVERRIDE Defines an alternate location of shard.override.yml.
shard.yml Describes a shard project including its dependencies. See shard.yml(5) for documentation.
shard.override.yml Allows overriding the source and restriction of dependencies. An alternative location can be configured with the env var SHARDS_OVERRIDE.
The file contains a YAML document with a single dependencies key. It has the same semantics as in shard.yml. Dependency configuration takes precedence over the configuration in shard.yml or any dependency’s shard.yml.
Use cases are local working copies, forcing a specific dependency version despite mismatching constraints, fixing a dependency, checking compatibility with unreleased dependency versions.
shard.lock Lockfile that stores information about the installed versions.
If your shard builds an application, shard.lock should be checked into version control to provide reproducible dependency installs.
If it is only a library for other shards to depend on, shard.lock should not be checked in, only shard.yml. It’s good advice to add it to .gitignore.
Report shards bugs to https://github.com/crystal-lang/shards/issues
Crystal Language home page: https://crystal-lang.org
Copyright © 2021 Julien Portalier.
License Apache 2.0 <http://www.apache.org/licenses/LICENSE-2.0>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
Written by Julien Portalier and the Crystal project.
shard.yml(5)
OGRINFO(1)                            GDAL                            OGRINFO(1)
ogrinfo - Lists information about an OGR-supported data source.
ogrinfo [--help-general] [-ro] [-q] [-where restricted_where|\@filename] [-spat xmin ymin xmax ymax] [-geomfield field] [-fid fid] [-sql statement|\@filename] [-dialect dialect] [-al] [-rl] [-so] [-fields={YES/NO}] [-geom={YES/NO/SUMMARY/WKT/ISO_WKT}] [--formats] [[-oo NAME=VALUE] ...] [-nomd] [-listmdd] [-mdd domain|`all`]* [-nocount] [-noextent] [-nogeomtype] [-wkt_format WKT1|WKT2|...] [-fielddomain name] <datasource_name> [<layer> [<layer> ...]]
The ogrinfo program lists various information about an OGR-supported data source to stdout (the terminal). By executing SQL statements it is also possible to edit data.
-ro    Open the data source in read-only mode.
-al    List all features of all layers (used instead of having to give layer names as arguments).
-rl    Enable random layer reading mode, i.e. iterate over features in the order they are found in the dataset, and not layer per layer. This can be significantly faster for some formats (for example OSM, GMLAS).
-so    Summary Only: suppress listing of individual features and show only summary information like projection, schema, feature count and extents.
-q     Quiet verbose reporting of various information, including coordinate system, layer schema, extents, and feature count.
-where <restricted_where> An attribute query in a restricted form of the queries used in the SQL WHERE statement. Only features matching the attribute query will be reported. Starting with GDAL 2.1, the \filename syntax can be used to indicate that the content is in the pointed filename.
-sql <statement> Execute the indicated SQL statement and return the result. Starting with GDAL 2.1, the @filename syntax can be used to indicate that the content is in the pointed filename. Data can also be edited with SQL INSERT, UPDATE, DELETE, DROP TABLE, ALTER TABLE etc. Editing capabilities depend on the selected dialect.
-spat <xmin> <ymin> <xmax> <ymax> The area of interest. Only features within the rectangle will be reported.
-geomfield <field> Name of the geometry field on which the spatial filter operates.
-fid <fid> If provided, only the feature with this feature id will be reported.  Operates exclusive of the spatial or attribute queries. Note: if you want to select several features based on their feature id, you can also use the fact the 'fid' is a special field recognized by OGR SQL. So, -where "fid in (1,3,5)" would select features 1, 3 and 5.
-fields YES|NO: If set to NO, the feature dump will not display field values. Default value is YES.
-fielddomain <domain_name> New in version 3.3.
Display details about a field domain.
-geom YES|NO|SUMMARY|WKT|ISO_WKT If set to NO, the feature dump will not display the geometry. If set to SUMMARY, only a summary of the geometry will be displayed. If set to YES or ISO_WKT, the geometry will be reported in full OGC WKT format.  If set to WKT the geometry will be reported in legacy WKT. Default value is YES. (WKT and ISO_WKT are available starting with GDAL 2.1, which also changes the default to ISO_WKT)
-oo NAME=VALUE Dataset open option (format-specific)
-nomd  Suppress metadata printing. Some datasets may contain a lot of metadata strings.
-listmdd List all metadata domains available for the dataset.
-mdd <domain> Report metadata for the specified domain. all can be used to report metadata in all domains.
-nocount Suppress feature count printing.
-noextent Suppress spatial extent printing.
-nogeomtype Suppress layer geometry type printing.
New in version 3.1.
--formats List the format drivers that are enabled.
-wkt_format <format> The WKT format used to display the SRS.  Currently supported values for the format are:
WKT1
WKT2 (latest WKT version, currently WKT2_2018)
WKT2_2015
WKT2_2018
New in version 3.0.0.
<datasource_name> The data source to open. May be a filename, directory or other virtual name. See the OGR Vector Formats list for supported datasources.
<layer> One or more layer names may be reported.  If no layer names are passed then ogrinfo will report a list of available layers (and their layer wide geometry type). If layer name(s) are given then their extents, coordinate system, feature count, geometry type, schema and all features matching query parameters will be reported to the terminal. If no query parameters are provided, all features are reported.
Geometries are reported in OGC WKT format.
Example of reporting the names of the layers in a NTF file:
ogrinfo wrk/SHETLAND_ISLANDS.NTF
# INFO: Open of `wrk/SHETLAND_ISLANDS.NTF' # using driver `UK .NTF' successful. # 1: BL2000_LINK (Line String) # 2: BL2000_POLY (None) # 3: BL2000_COLLECTIONS (None) # 4: FEATURE_CLASSES (None)
Example of retrieving a summary (-so) of a layer without showing details about every single feature:
ogrinfo \ -so \ natural_earth_vector.gpkg \ ne_10m_admin_0_antarctic_claim_limit_lines
# INFO: Open of `natural_earth_vector.gpkg' #      using driver `GPKG' successful.
# Layer name: ne_10m_admin_0_antarctic_claim_limit_lines # Geometry: Line String # Feature Count: 23 # Extent: (-150.000000, -90.000000) - (160.100000, -60.000000) # Layer SRS WKT: # GEOGCS["WGS 84", #     DATUM["WGS_1984", #         SPHEROID["WGS 84",6378137,298.257223563, #             AUTHORITY["EPSG","7030"]], #         AUTHORITY["EPSG","6326"]], #     PRIMEM["Greenwich",0, #         AUTHORITY["EPSG","8901"]], #     UNIT["degree",0.0174532925199433, #         AUTHORITY["EPSG","9122"]], #     AUTHORITY["EPSG","4326"]] # FID Column = fid # Geometry Column = geom # type: String (15.0) # scalerank: Integer (0.0) # featurecla: String (50.0)
Example of using an attribute query to restrict the output of the features in a layer:
ogrinfo -ro \ -where 'GLOBAL_LINK_ID=185878' \ wrk/SHETLAND_ISLANDS.NTF BL2000_LINK
# INFO: Open of `wrk/SHETLAND_ISLANDS.NTF' # using driver `UK .NTF' successful. # # Layer name: BL2000_LINK # Geometry: Line String # Feature Count: 1 # Extent: (419794.100000, 1069031.000000) - (419927.900000, 1069153.500000) # Layer SRS WKT: # PROJCS["OSGB 1936 / British National Grid", # GEOGCS["OSGB 1936", # DATUM["OSGB_1936", # SPHEROID["Airy 1830",6377563.396,299.3249646]], # PRIMEM["Greenwich",0], # UNIT["degree",0.0174532925199433]], # PROJECTION["Transverse_Mercator"], # PARAMETER["latitude_of_origin",49], # PARAMETER["central_meridian",-2], # PARAMETER["scale_factor",0.999601272], # PARAMETER["false_easting",400000], # PARAMETER["false_northing",-100000], # UNIT["metre",1]] # LINE_ID: Integer (6.0) # GEOM_ID: Integer (6.0) # FEAT_CODE: String (4.0) # GLOBAL_LINK_ID: Integer (10.0) # TILE_REF: String (10.0) # OGRFeature(BL2000_LINK):2 # LINE_ID (Integer) = 2 # GEOM_ID (Integer) = 2 # FEAT_CODE (String) = (null) # GLOBAL_LINK_ID (Integer) = 185878 # TILE_REF (String) = SHETLAND I # LINESTRING (419832.100 1069046.300,419820.100 1069043.800,419808.300 # 1069048.800,419805.100 1069046.000,419805.000 1069040.600,419809.400 # 1069037.400,419827.400 1069035.600,419842 1069031,419859.000 # 1069032.800,419879.500 1069049.500,419886.700 1069061.400,419890.100 # 1069070.500,419890.900 1069081.800,419896.500 1069086.800,419898.400 # 1069092.900,419896.700 1069094.800,419892.500 1069094.300,419878.100 # 1069085.600,419875.400 1069087.300,419875.100 1069091.100,419872.200 # 1069094.600,419890.400 1069106.400,419907.600 1069112.800,419924.600 # 1069133.800,419927.900 1069146.300,419927.600 1069152.400,419922.600 # 1069153.500,419917.100 1069153.500,419911.500 1069153.000,419908.700 # 1069152.500,419903.400 1069150.800,419898.800 1069149.400,419894.800 # 1069149.300,419890.700 1069149.400,419890.600 1069149.400,419880.800 # 1069149.800,419876.900 1069148.900,419873.100 1069147.500,419870.200 # 1069146.400,419862.100 1069143.000,419860 1069142,419854.900 # 1069138.600,419850 1069135,419848.800 1069134.100,419843 # 1069130,419836.200 1069127.600,419824.600 1069123.800,419820.200 # 1069126.900,419815.500 1069126.900,419808.200 1069116.500,419798.700 # 1069117.600,419794.100 1069115.100,419796.300 1069109.100,419801.800 # 1069106.800,419805.000  1069107.300)
Example of updating a value of an attribute in a shapefile with SQL by using the SQLite dialect:
ogrinfo test.shp -dialect sqlite -sql "update test set attr='bar' where attr='foo'"
SS-LOCAL(1)                 Shadowsocks-libev Manual                 SS-LOCAL(1)
ss-local - shadowsocks client as socks5 proxy, libev port
ss-local [-uv6] [-h|--help] [-s <server_host>] [-p <server_port>] [-l <local_port>] [-k <password>] [-m <encrypt_method>] [-f <pid_file>] [-t <timeout>] [-c <config_file>] [-i <interface>] [-a <user_name>] [-b <local_address>] [-n <nofile>] [--fast-open] [--reuse-port] [--acl <acl_config>] [--mtu <MTU>] [--no-delay] [--plugin <plugin_name>] [--plugin-opts <plugin_options>] [--password <password>] [--key <key_in_base64>]
Shadowsocks-libev is a lightweight and secure socks5 proxy. It is a port of the original shadowsocks created by clowwindy. Shadowsocks-libev is written in pure C and takes advantage of libev to achieve both high performance and low resource consumption.
Shadowsocks-libev consists of five components. ss-local(1) works as a standard socks5 proxy on local machines to proxy TCP traffic. For more information, check out shadowsocks-libev(8).
-s <server_host> Set the server’s hostname or IP.
-p <server_port> Set the server’s port number.
-l <local_port> Set the local port number.
-k <password>, --password <password> Set the password. The server and the client should use the same password.
--key <key_in_base64> Set the key directly. The key should be encoded with URL-safe Base64.
-m <encrypt_method> Set the cipher.
Shadowsocks-libev accepts 19 different ciphers:
aes-128-gcm, aes-192-gcm, aes-256-gcm, rc4-md5, aes-128-cfb, aes-192-cfb, aes-256-cfb, aes-128-ctr, aes-192-ctr, aes-256-ctr, bf-cfb, camellia-128-cfb, camellia-192-cfb, camellia-256-cfb, chacha20-ietf-poly1305, xchacha20-ietf-poly1305, salsa20, chacha20 and chacha20-ietf.
The default cipher is chacha20-ietf-poly1305.
If built with PolarSSL or custom OpenSSL libraries, some of these ciphers may not work.
-a <user_name> Run as a specific user.
-f <pid_file> Start shadowsocks as a daemon with specific pid file.
-t <timeout> Set the socket timeout in seconds. The default value is 60.
-c <config_file> Use a configuration file.
Refer to shadowsocks-libev(8) CONFIG FILE section for more details.
-n <number> Specify max number of open files.
Only available on Linux.
-i <interface> Send traffic through specific network interface.
For example, there are three interfaces in your device, which is lo (127.0.0.1), eth0 (192.168.0.1) and eth1 (192.168.0.2). Meanwhile, you configure ss-local to listen on 0.0.0.0:8388 and bind to eth1. That results the traffic go out through eth1, but not lo nor eth0. This option is useful to control traffic in multi-interface environment.
-b <local_address> Specify the local address to use while this client is making outbound connections to the server.
-u Enable UDP relay.
-U Enable UDP relay and disable TCP relay.
-6 Resovle hostname to IPv6 address first.
--fast-open Enable TCP fast open.
Only available with Linux kernel > 3.7.0.
--reuse-port Enable port reuse.
Only available with Linux kernel > 3.9.0.
--acl <acl_config> Enable ACL (Access Control List) and specify config file.
--mtu <MTU> Specify the MTU of your network interface.
--mptcp Enable Multipath TCP.
Only available with MPTCP enabled Linux kernel.
--no-delay Enable TCP_NODELAY.
--plugin <plugin_name> Enable SIP003 plugin. (Experimental)
--plugin-opts <plugin_options> Set SIP003 plugin options. (Experimental)
-v Enable verbose mode.
-h|--help Print help message.
ss-local(1) can be started from command line and run in foreground. Here is an example:
# Start ss-local with given parameters ss-local -s example.com -p 12345 -l 1080 -k foobar -m aes-256-cfb
ss-server(1), ss-tunnel(1), ss-redir(1), ss-manager(1), shadowsocks-libev(8), iptables(8), /etc/shadowsocks-libev/config.json
7zr(1)                       General Commands Manual                      7zr(1)
7zr - A file archiver with highest compression ratio
7zr [adeltux] [-] [SWITCH] <ARCHIVE_NAME> <ARGUMENTS>...
7zr is a stand-alone executable. 7zr handles less archive formats than 7z, but does not need any others. 7zr is a "light-version" of 7za that only handles 7z archives.
-si    Read data from StdIn (eg: tar cf - directory | 7zr a -si directory.tar.7z)
-so    Write data to StdOut (eg: 7zr x -so directory.tar.7z | tar xf -)
On Linux/Unix, in order to backup directories you must use tar : - to backup a directory  : tar cf - directory | 7zr a -si directory.tar.7z - to restore your backup : 7zr x -so directory.tar.7z | tar xf -
example : 7zr a directory.7z  directory
EXAMPLE 1 7zr a -t7z -m0=lzma -mx=9 -mfb=64 -md=32m -ms=on archive.7z dir1 adds all files from directory "dir1" to archive archive.7z using "ultra settings"
EXAMPLE 2 7zr a -sfx archive.exe dir1 add all files from directory "dir1" to SFX archive archive.exe (Remark : SFX archive MUST end with ".exe")
EXAMPLE 3 7zr a -mhe=on -pmy_password archive.7z a_directory add all files from directory "a_directory" to the archive "archive.7z" (with data and header archive encryption on)
7z(1), 7za(1), bzip2(1), gzip(1), zip(1)
FIND(1)                      General Commands Manual                     FIND(1)
find - search for files in a directory hierarchy
find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point...] [expression]
This manual page documents the GNU version of find.  GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name.  If no starting-point is specified, `.' is assumed.
If you are using find in an environment where security is important (for example if you are using it to search directories that are writable by other users), you should read the `Security Considerations' chapter of the findutils documentation, which is called Finding Files and comes with findutils.  That document also includes a lot more detail and discussion than this manual page, so you may find it a more useful source of information.
The -H, -L and -P options control the treatment of symbolic links. Command-line arguments following these are taken to be names of files or directories to be examined, up to the first argument that begins with `-', or the argument `(' or `!'.  That argument and any following arguments are taken to be the expression describing what is to be searched for.  If no paths are given, the current directory is used.  If no expression is given, the expression -print is used (but you should probably consider using -print0 instead, anyway).
This manual page talks about `options' within the expression list.  These options control the behaviour of find but are specified immediately after the last path name.  The five `real' options -H, -L, -P, -D and -O must appear before the first path name, if at all.  A double dash -- could theoretically be used to signal that any remaining arguments are not options, but this does not really work due to the way find determines the end of the following path arguments: it does that by reading until an expression argument comes (which also starts with a `-').  Now, if a path argument would start with a `-', then find would treat it as expression argument instead.  Thus, to ensure that all start points are taken as such, and especially to prevent that wildcard patterns expanded by the calling shell are not mistakenly treated as expression arguments, it is generally safer to prefix wildcards or dubious path names with either `./' or to use absolute path names starting with '/'.
-P     Never follow symbolic links.  This is the default behaviour.  When find examines or prints information about files, and the file is a symbolic link, the information used shall be taken from the properties of the symbolic link itself.
-L     Follow symbolic links.  When find examines or prints information about files, the information used shall be taken from the properties of the file to which the link points, not from the link itself (unless it is a broken symbolic link or find is unable to examine the file to which the link points).  Use of this option implies -noleaf.  If you later use the -P option, -noleaf will still be in effect.  If -L is in effect and find discovers a symbolic link to a subdirectory during its search, the subdirectory pointed to by the symbolic link will be searched.
When the -L option is in effect, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself (unless the symbolic link is broken). Actions that can cause symbolic links to become broken while find is executing (for example -delete) can give rise to confusing behaviour.  Using -L causes the -lname and -ilname predicates always to return false.
-H     Do not follow symbolic links, except while processing the command line arguments.  When find examines or prints information about files, the information used shall be taken from the properties of the symbolic link itself.  The only exception to this behaviour is when a file specified on the command line is a symbolic link, and the link can be resolved.  For that situation, the information used is taken from whatever the link points to (that is, the link is followed).  The information about the link itself is used as a fallback if the file pointed to by the symbolic link cannot be examined.  If -H is in effect and one of the paths specified on the command line is a symbolic link to a directory, the contents of that directory will be examined (though of course -maxdepth 0 would prevent this).
If more than one of -H, -L and -P is specified, each overrides the others; the last one appearing on the command line takes effect.  Since it is the default, the -P option should be considered to be in effect unless either -H or -L is specified.
GNU find frequently stats files during the processing of the command line itself, before any searching has begun.  These options also affect how those arguments are processed.  Specifically, there are a number of tests that compare files listed on the command line against a file we are currently considering.  In each case, the file specified on the command line will have been examined and some of its properties will have been saved.  If the named file is in fact a symbolic link, and the -P option is in effect (or if neither -H nor -L were specified), the information used for the comparison will be taken from the properties of the symbolic link.  Otherwise, it will be taken from the properties of the file the link points to.  If find cannot follow the link (for example because it has insufficient privileges or the link points to a nonexistent file) the properties of the link itself will be used.
When the -H or -L options are in effect, any symbolic links listed as the argument of -newer will be dereferenced, and the timestamp will be taken from the file to which the symbolic link points.  The same consideration applies to -newerXY, -anewer and -cnewer.
The -follow option has a similar effect to -L, though it takes effect at the point where it appears (that is, if -L is not used but -follow is, any symbolic links appearing after -follow on the command line will be dereferenced, and those before it will not).
-D debugopts Print diagnostic information; this can be helpful to diagnose problems with why find is not doing what you want.  The list of debug options should be comma separated.  Compatibility of the debug options is not guaranteed between releases of findutils. For a complete list of valid debug options, see the output of find -D help.  Valid debug options include
exec   Show diagnostic information relating to -exec, -execdir, -ok and -okdir
opt    Prints diagnostic information relating to the optimisation of the expression tree; see the -O option.
rates  Prints a summary indicating how often each predicate succeeded or failed.
search Navigate the directory tree verbosely.
stat   Print messages as files are examined with the stat and lstat system calls.  The find program tries to minimise such calls.
tree   Show the expression tree in its original and optimised form.
all    Enable all of the other debug options (but help).
help   Explain the debugging options.
-Olevel Enables query optimisation.  The find program reorders tests to speed up execution while preserving the overall effect; that is, predicates with side effects are not reordered relative to each other.  The optimisations performed at each optimisation level are as follows.
0      Equivalent to optimisation level 1.
1      This is the default optimisation level and corresponds to the traditional behaviour.  Expressions are reordered so that tests based only on the names of files (for example -name and -regex) are performed first.
2      Any -type or -xtype tests are performed after any tests based only on the names of files, but before any tests that require information from the inode.  On many modern versions of Unix, file types are returned by readdir() and so these predicates are faster to evaluate than predicates which need to stat the file first.  If you use the -fstype FOO predicate and specify a filesystem type FOO which is not known (that is, present in `/etc/mtab') at the time find starts, that predicate is equivalent to -false.
3      At this optimisation level, the full cost-based query optimiser is enabled.  The order of tests is modified so that cheap (i.e. fast) tests are performed first and more expensive ones are performed later, if necessary.  Within each cost band, predicates are evaluated earlier or later according to whether they are likely to succeed or not. For -o, predicates which are likely to succeed are evaluated earlier, and for -a, predicates which are likely to fail are evaluated earlier.
The cost-based optimiser has a fixed idea of how likely any given test is to succeed.  In some cases the probability takes account of the specific nature of the test (for example, -type f is assumed to be more likely to succeed than -type c).  The cost- based optimiser is currently being evaluated.  If it does not actually improve the performance of find, it will be removed again.  Conversely, optimisations that prove to be reliable, robust and effective may be enabled at lower optimisation levels over time.  However, the default behaviour (i.e. optimisation level 1) will not be changed in the 4.3.x release series.  The findutils test suite runs all the tests on find at each optimisation level and ensures that the result is the same.
The part of the command line after the list of starting points is the expression.  This is a kind of query specification describing how we match files and what we do with the files that were matched.  An expression is composed of a sequence of things:
Tests  Tests return a true or false value, usually on the basis of some property of a file we are considering.  The -empty test for example is true only when the current file is empty.
Actions Actions have side effects (such as printing something on the standard output) and return either true or false, usually based on whether or not they are successful.  The -print action for example prints the name of the current file on the standard output.
Global options Global options affect the operation of tests and actions specified on any part of the command line.  Global options always return true.  The -depth option for example makes find traverse the file system in a depth-first order.
Positional options Positional options affect only tests or actions which follow them. Positional options always return true.  The -regextype option for example is positional, specifying the regular expression dialect for regular expressions occurring later on the command line.
Operators Operators join together the other items within the expression. They include for example -o (meaning logical OR) and -a (meaning logical AND).  Where an operator is missing, -a is assumed.
The -print action is performed on all files for which the whole expression is true, unless it contains an action other than -prune or -quit.  Actions which inhibit the default -print are -delete, -exec, -execdir, -ok, -okdir, -fls, -fprint, -fprintf, -ls, -print and -printf.
The -delete action also acts like an option (since it implies -depth).
POSITIONAL OPTIONS Positional options always return true.  They affect only tests occurring later on the command line.
-daystart Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago. This option only affects tests which appear later on the command line.
-follow Deprecated; use the -L option instead.  Dereference symbolic links.  Implies -noleaf.  The -follow option affects only those tests which appear after it on the command line.  Unless the -H or -L option has been specified, the position of the -follow option changes the behaviour of the -newer predicate; any files listed as the argument of -newer will be dereferenced if they are symbolic links.  The same consideration applies to -newerXY, -anewer and -cnewer.  Similarly, the -type predicate will always match against the type of the file that a symbolic link points to rather than the link itself.  Using -follow causes the -lname and -ilname predicates always to return false.
-regextype type Changes the regular expression syntax understood by -regex and -iregex tests which occur later on the command line.  To see which regular expression types are known, use -regextype help.  The Texinfo documentation (see SEE ALSO) explains the meaning of and differences between the various types of regular expression.
-warn, -nowarn Turn warning messages on or off.  These warnings apply only to the command line usage, not to any conditions that find might encounter when it searches directories.  The default behaviour corresponds to -warn if standard input is a tty, and to -nowarn otherwise.  If a warning message relating to command-line usage is produced, the exit status of find is not affected.  If the POSIXLY_CORRECT environment variable is set, and -warn is also used, it is not specified which, if any, warnings will be active.
GLOBAL OPTIONS Global options always return true.  Global options take effect even for tests which occur earlier on the command line.  To prevent confusion, global options should specified on the command-line after the list of start points, just before the first test, positional option or action. If you specify a global option in some other place, find will issue a warning message explaining that this can be confusing.
The global options occur after the list of start points, and so are not the same kind of option as -L, for example.
-d     A synonym for -depth, for compatibility with FreeBSD, NetBSD, MacOS X and OpenBSD.
-depth Process each directory's contents before the directory itself. The -delete action also implies -depth.
-help, --help Print a summary of the command-line usage of find and exit.
-ignore_readdir_race Normally, find will emit an error message when it fails to stat a file.  If you give this option and a file is deleted between the time find reads the name of the file from the directory and the time it tries to stat the file, no error message will be issued. This also applies to files or directories whose names are given on the command line.  This option takes effect at the time the command line is read, which means that you cannot search one part of the filesystem with this option on and part of it with this option off (if you need to do that, you will need to issue two find commands instead, one with the option and one without it).
Furthermore, find with the -ignore_readdir_race option will ignore errors of the -delete action in the case the file has disappeared since the parent directory was read: it will not output an error diagnostic, and the return code of the -delete action will be true.
-maxdepth levels Descend at most levels (a non-negative integer) levels of directories below the starting-points.  Using -maxdepth 0 means only apply the tests and actions to the starting-points themselves.
-mindepth levels Do not apply any tests or actions at levels less than levels (a non-negative integer).  Using -mindepth 1 means process all files except the starting-points.
-mount Don't descend directories on other filesystems.  An alternate name for -xdev, for compatibility with some other versions of find.
-noignore_readdir_race Turns off the effect of -ignore_readdir_race.
-noleaf Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count.  This option is needed when searching filesystems that do not follow the Unix directory- link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points.  Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory.  When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree).  If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed.
-version, --version Print the find version number and exit.
-xdev  Don't descend directories on other filesystems.
TESTS Some tests, for example -newerXY and -samefile, allow comparison between the file currently being examined and some reference file specified on the command line.  When these tests are used, the interpretation of the reference file is determined by the options -H, -L and -P and any previous -follow, but the reference file is only examined once, at the time the command line is parsed.  If the reference file cannot be examined (for example, the stat(2) system call fails for it), an error message is issued, and find exits with a nonzero status.
A numeric argument n can be specified to tests (like -amin, -mtime, -gid, -inum, -links, -size, -uid and -used) as
+n     for greater than n,
-n     for less than n,
n      for exactly n.
Supported tests:
-amin n File was last accessed less than, more than or exactly n minutes ago.
-anewer reference Time of the last access of the current file is more recent than that of the last data modification of the reference file.  If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used.
-atime n File was last accessed less than, more than or exactly n*24 hours ago.  When find figures out how many 24-hour periods ago the file was last accessed, any fractional part is ignored, so to match -atime +1, a file has to have been accessed at least two days ago.
-cmin n File's status was last changed less than, more than or exactly n minutes ago.
-cnewer reference Time of the last status change of the current file is more recent than that of the last data modification of the reference file.  If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used.
-ctime n File's status was last changed less than, more than or exactly n*24 hours ago.  See the comments for -atime to understand how rounding affects the interpretation of file status change times.
-empty File is empty and is either a regular file or a directory.
-executable Matches files which are executable and directories which are searchable (in a file name resolution sense) by the current user. This takes into account access control lists and other permissions artefacts which the -perm test ignores.  This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server.  Because this test is based only on the result of the access(2) system call, there is no guarantee that a file for which this test succeeds can actually be executed.
-false Always false.
-fstype type File is on a filesystem of type type.  The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K.  You can use -printf with the %F directive to see the types of your filesystems.
-gid n File's numeric group ID is less than, more than or exactly n.
-group gname File belongs to group gname (numeric group ID allowed).
-ilname pattern Like -lname, but the match is case insensitive.  If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken.
-iname pattern Like -name, but the match is case insensitive.  For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc.  The pattern `*foo*` will also match a file called '.foobar'.
-inum n File has inode number smaller than, greater than or exactly n.  It is normally easier to use the -samefile test instead.
-ipath pattern Like -path.  but the match is case insensitive.
-iregex pattern Like -regex, but the match is case insensitive.
-iwholename pattern See -ipath.  This alternative is less portable than -ipath.
-links n File has less than, more than or exactly n hard links.
-lname pattern File is a symbolic link whose contents match shell pattern pattern.  The metacharacters do not treat `/' or `.' specially. If the -L option or the -follow option is in effect, this test returns false unless the symbolic link is broken.
-mmin n File's data was last modified less than, more than or exactly n minutes ago.
-mtime n File's data was last modified less than, more than or exactly n*24 hours ago.  See the comments for -atime to understand how rounding affects the interpretation of file modification times.
-name pattern Base of file name (the path with the leading directories removed) matches shell pattern pattern.  Because the leading directories are removed, the file names considered for a match with -name will never include a slash, so `-name a/b' will never match anything (you probably need to use -path instead).  A warning is issued if you try to do this, unless the environment variable POSIXLY_CORRECT is set.  The metacharacters (`*', `?', and `[]') match a `.' at the start of the base name (this is a change in findutils-4.2.2; see section STANDARDS CONFORMANCE below).  To ignore a directory and the files under it, use -prune rather than checking every file in the tree; see an example in the description of that action.  Braces are not recognised as being special, despite the fact that some shells including Bash imbue braces with a special meaning in shell patterns.  The filename matching is performed with the use of the fnmatch(3) library function.  Don't forget to enclose the pattern in quotes in order to protect it from expansion by the shell.
-newer reference Time of the last data modification of the current file is more recent than that of the last data modification of the reference file.  If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used.
-newerXY reference Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference.  The letters X and Y can be any of the following letters:
a   The access time of the file reference B   The birth time of the file reference c   The inode status change time of reference m   The modification time of the file reference t   reference is interpreted directly as a time
Some combinations are invalid; for example, it is invalid for X to be t.  Some combinations are not implemented on all systems; for example B is not supported on all systems.  If an invalid or unsupported combination of XY is specified, a fatal error results. Time specifications are interpreted as for the argument to the -d option of GNU date.  If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results.  If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown.
-nogroup No group corresponds to file's numeric group ID.
-nouser No user corresponds to file's numeric user ID.
-path pattern File name matches shell pattern pattern.  The metacharacters do not treat `/' or `.' specially; so, for example, find . -path "./sr*sc" will print an entry for a directory called ./src/misc (if one exists).  To ignore a whole directory tree, use -prune rather than checking every file in the tree.  Note that the pattern match test applies to the whole file name, starting from one of the start points named on the command line.  It would only make sense to use an absolute path name here if the relevant start point is also an absolute path.  This means that this command will never match anything: find bar -path /foo/bar/myfile -print Find compares the -path argument with the concatenation of a directory name and the base name of the file it's examining. Since the concatenation will never end with a slash, -path arguments ending in a slash will match nothing (except perhaps a start point specified on the command line).  The predicate -path is also supported by HP-UX find and is part of the POSIX 2008 standard.
-perm mode File's permission bits are exactly mode (octal or symbolic). Since an exact match is required, if you want to use this form for symbolic modes, you may have to specify a rather complex mode string.  For example `-perm g=w' will only match files which have mode 0020 (that is, ones for which group write permission is the only permission set).  It is more likely that you will want to use the `/' or `-' forms, for example `-perm -g=w', which matches any file with group write permission.  See the EXAMPLES section for some illustrative examples.
-perm -mode All of the permission bits mode are set for the file.  Symbolic modes are accepted in this form, and this is usually the way in which you would want to use them.  You must specify `u', `g' or `o' if you use a symbolic mode.  See the EXAMPLES section for some illustrative examples.
-perm /mode Any of the permission bits mode are set for the file.  Symbolic modes are accepted in this form.  You must specify `u', `g' or `o' if you use a symbolic mode.  See the EXAMPLES section for some illustrative examples.  If no permission bits in mode are set, this test matches any file (the idea here is to be consistent with the behaviour of -perm -000).
-perm +mode This is no longer supported (and has been deprecated since 2005). Use -perm /mode instead.
-readable Matches files which are readable by the current user.  This takes into account access control lists and other permissions artefacts which the -perm test ignores.  This test makes use of the access(2) system call, and so can be fooled by NFS servers which do UID mapping (or root-squashing), since many systems implement access(2) in the client's kernel and so cannot make use of the UID mapping information held on the server.
-regex pattern File name matches regular expression pattern.  This is a match on the whole path, not a search.  For example, to match a file named ./fubar3, you can use the regular expression `.*bar.' or `.*b.*3', but not `f.*r3'.  The regular expressions understood by find are by default Emacs Regular Expressions (except that `.' matches newline), but this can be changed with the -regextype option.
-samefile name File refers to the same inode as name.  When -L is in effect, this can include symbolic links.
-size n[cwbkMG] File uses less than, more than or exactly n units of space, rounding up.  The following suffixes can be used:
`b'    for 512-byte blocks (this is the default if no suffix is used)
`c'    for bytes
`w'    for two-byte words
`k'    for kibibytes (KiB, units of 1024 bytes)
`M'    for mebibytes (MiB, units of 1024 * 1024 = 1048576 bytes)
`G'    for gibibytes (GiB, units of 1024 * 1024 * 1024 = 1073741824 bytes)
The size is simply the st_size member of the struct stat populated by the lstat (or stat) system call, rounded up as shown above.  In other words, it's consistent with the result you get for ls -l. Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently.  The `b' suffix always denotes 512-byte blocks and never 1024-byte blocks, which is different to the behaviour of -ls.
The + and - prefixes signify greater than and less than, as usual; i.e., an exact size of n units does not match.  Bear in mind that the size is rounded up to the next unit.  Therefore -size -1M is not equivalent to -size -1048576c.  The former only matches empty files, the latter matches files from 0 to 1,048,575 bytes.
-true  Always true.
-type c File is of type c:
b      block (buffered) special
c      character (unbuffered) special
d      directory
p      named pipe (FIFO)
f      regular file
l      symbolic link; this is never true if the -L option or the -follow option is in effect, unless the symbolic link is broken.  If you want to search for symbolic links when -L is in effect, use -xtype.
s      socket
D      door (Solaris)
To search for more than one type at once, you can supply the combined list of type letters separated by a comma `,' (GNU extension).
-uid n File's numeric user ID is less than, more than or exactly n.
-used n File was last accessed less than, more than or exactly n days after its status was last changed.
-user uname File is owned by user uname (numeric user ID allowed).