Standardization is important for programmers, administrators and users alike.
They all expect their programms, scripts and worflows to operate „normally“ after an update or even between various versions of Linux.
What people hate about „change“ is they have to relearn (takes time and energy – brain loves to save energy) – how to do previously done tasks.
While it is of course important to improve on „what concepts makes sense“, workflow and recognize one’s (design or implementation) errors and correct them to reach the 99% perfection that is possible.
Stability, Security, Efficiency (Speed)… can save time – and time is what computers have more than humans. So they should boot up fast shutdown fast and be good tools that serve 99% of the people – create real value – create real progress (fake progress is the same iphone in a new color) – and not serve as NSA mass surveillance programs only.
John F. Kennedy: „An error only becomes an mistake – if you refuse to correct it.“
We all have to adapt to a ever changing world – increasingly changed by ourselves – to the better or to the worse – is up to every one of us and his/her level of knowledge and consciousness.
If some closed-source company decides to change it’s wordings, namings and GUI with every version… go ahead. The rest: Don’t!
It is like: „here have the same massively fuel consuming car – but with new color and we replaced the steering wheel with a joystick.“
While some may say „cool“ and think it is fun to adapt to those new workflows – the rest will say „shiiiit“ 😀
I think it would also be interesting to see an „Open Hardware Definition/Standard“ – that standardizes hardware (v1..v2..v3) that is fully supported by free software (no closed source drivers/firmware/binary blobs!) by the Linux-Standard and therefore guranteed to work „out of the box“ – or as Steve Jobs put it – „it just works“.
more standards: http://refspecs.linuxfoundation.org/FHS_2.3/fhs-2.3.html (discuss)
Apple did two things right: 0. innovation 1. standardize hardware 2. software quality 3. ease of use (also resulting partly out of the points 0-2) … lately those 4 points have been replaced by: 0. sell 1. sell. 2. sell more no matter what. I will NEVER upgrade my 10 year old macmini EVER. It does Sound and Video and that’s all i use it for.
Linux as Unix is a/should be standardized Operating System… the standard documentation is called POSIX and a copy is available online (thanks) – but various groups hold copyrights. So the standard itself is NOT GPL.
Similar to „Java“ or „ECMAScript“ which is – at the very beginning – also just a definition of an programming language. But as far as i know everyone is allowed to implement this standard to his/her liking – this is true for Java, ECMA and Linux/Unix – hence the multifold distributions and versions.
- UNIX ® is a registered Trademark of The Open Group.
- POSIX ® is a registered Trademark of The IEEE.
- Copyright © 2001-2016 The IEEE and The Open Group, All Rights Reserved
But it’s the same as with software – only god and nobody are perfect – anybody else is not.
So you HAVE to expect any standard and any software will contain errors/mistakes.
All you can do is – do define test-cases – work through them before release and incrementally work towards the possible 99% perfection and standard and software quality.
It is interesting to note that some versions of Linux such as the very ressource-minimalistic (for rouers) BusyBox – is NOT implementing the full standard – so you will have to operate with a very stripped down command-set there. (AVM(FritzBox) and QNAP using BusyBox)
# you can choose what manpage to see 1 or 1p (Programmer's Manual)
# 1 = manpage for ls
# 1p = the IEEE copyrighted (not GPL!) definition of the POSIX standard that also defines linux commans such as ls
Basically, the linux manuals are documentation of the commands/APIs from their writers; The POSIX manuals are from the POSIX standard. Usually, the „normal“ ones are shorter and terser, but deal with the specific implementation; the POSIX ones are longer and more detailed (see
), but only tell what is in the standard.
The best is to look in both.
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines the application programming interface (API), along with command line shells and utility interfaces, for software compatibility with variants of Unix and other operating systems.
POSIX.1-2008 (with two TCs)
As of 2017, Base Specifications, Issue 7 (or IEEE Std 1003.1-2008, 2016 Edition) represents the current version. A free online copy is available.
POSIX.1-2008 defines a standard operating system interface and environment, including a command interpreter (or “shell”), and common utility programs to support applications portability at the source code level.
POSIX.1-2008 is intended to be used by both application developers and system implementors and comprises four major components (each in an associated volume):
- General terms, concepts, and interfaces common to all volumes of this standard, including utility conventions and C-language header definitions, are included in the Base Definitions volume.
- Definitions for system service functions and subroutines, language-specific system services for the C programming language, function issues, including portability, error handling, and error recovery, are included in the System Interfaces volume.
- Definitions for a standard source code-level interface to command interpretation services (a “shell”) and common utility programs for application programs are included in the Shell and Utilities volume.
- Extended rationale that did not fit well into the rest of the document structure, which contains historical information concerning the contents of POSIX.1-2008 and why features were included or discarded by the standard developers, is included in the Rationale (Informative) volume.
The following areas are outside the scope of POSIX.1-2008:
- Graphics interfaces
- Database management system interfaces
- Record I/O considerations
- Object or binary code portability
- System configuration and resource availability
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
ls — list directory contents
ls [−ikqrs] [−glno] [−A|−a] [−C|−m|−x|−1] \
[−F|−p] [−H|−L] [−R|−d] [−S|−f|−t] [−c|−u] [file...]
For each operand that names a file of a type other than directory or
symbolic link to a directory, ls shall write the name of the file as
well as any requested, associated information. For each operand that
names a file of type directory, ls shall write the names of files
contained within the directory as well as any requested, associated
information. Filenames beginning with a ('.') and any
associated information shall not be written out unless explicitly
referenced, the −A or −a option is supplied, or an implementation-
defined condition causes them to be written. If one or more of the
−d, −F, or −l options are specified, and neither the −H nor the −L
option is specified, for each operand that names a file of type
symbolic link to a directory, ls shall write the name of the file as
well as any requested, associated information. If none of the −d, −F,
or −l options are specified, or the −H or −L options are specified,
for each operand that names a file of type symbolic link to a
directory, ls shall write the names of files contained within the
directory as well as any requested, associated information. In each
case where the names of files contained within a directory are
written, if the directory contains any symbolic links then ls shall
evaluate the file information and file type to be those of the
symbolic link itself, unless the −L option is specified.
If no operands are specified, ls shall behave as if a single operand
of dot ('.') had been specified. If more than one operand is
specified, ls shall write non-directory operands first; it shall sort
directory and non-directory operands separately according to the
collating sequence in the current locale.
The ls 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, ls shall write a
diagnostic message to standard error and shall either recover its
position in the hierarchy or terminate.
The ls utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
−A Write out all directory entries, including those whose
names begin with a ('.') but excluding the
entries dot and dot-dot (if they exist).
−C Write multi-text-column output with entries sorted down the
columns, according to the collating sequence. The number of
text columns and the column separator characters are
unspecified, but should be adapted to the nature of the
output device. This option disables long format output.
−F Do not follow symbolic links named as operands unless the
−H or −L options are specified. Write a ('/')
immediately after each pathname that is a directory, an
('*') after each that is executable, a
('|') after each that is a FIFO, and an at-
sign ('@') after each that is a symbolic link. For other
file types, other symbols may be written.
−H Evaluate the file information and file type for symbolic
links specified on the command line to be those of the file
referenced by the link, and not the link itself; however,
ls shall write the name of the link itself and not the file
referenced by the link.
−L Evaluate the file information and file type for all
symbolic links (whether named on the command line or
encountered in a file hierarchy) to be those of the file
referenced by the link, and not the link itself; however,
ls shall write the name of the link itself and not the file
referenced by the link. When −L is used with −l, write the
contents of symbolic links in the long format (see the
−R Recursively list subdirectories encountered. When a
symbolic link to a directory is encountered, the directory
shall not be recursively listed unless the −L option is
specified. The use of −R with −d or −f produces
−S Sort with the primary key being file size (in decreasing
order) and the secondary key being filename in the
collating sequence (in increasing order).
−a Write out all directory entries, including those whose
names begin with a ('.').
−c Use time of last modification of the file status
information (see the Base Definitions volume of
POSIX.1‐2008, sys_stat.h(0p)) instead of last modification
of the file itself for sorting (−t) or writing (−l).
−d Do not follow symbolic links named as operands unless the
−H or −L options are specified. Do not treat directories
differently than other types of files. The use of −d with
−R or −f produces unspecified results.
−f List the entries in directory operands in the order they
appear in the directory. The behavior for non-directory
operands is unspecified. This option shall turn on −a.
When −f is specified, any occurrences of the −r, −S, and −t
options shall be ignored and any occurrences of the −A, −g,
−l, −n, −o, and −s options may be ignored. The use of −f
with −R or −d produces unspecified results.
−g Turn on the −l (ell) option, but disable writing the file's
owner name or number. Disable the −C, −m, and −x options.
−i For each file, write the file's file serial number (see
stat() in the System Interfaces volume of POSIX.1‐2008).
−k Set the block size for the −s option and the per-directory
block count written for the −l, −n, −s, −g, and −o options
(see the STDOUT section) to 1024 bytes.
−l (The letter ell.) Do not follow symbolic links named as
operands unless the −H or −L options are specified. Write
out in long format (see the STDOUT section). Disable the
−C, −m, and −x options.
−m Stream output format; list pathnames across the page,
separated by a character followed by a
character. Use a character as the list terminator
and after the separator sequence when there is not room on
a line for the next list entry. This option disables long
−n Turn on the −l (ell) option, but when writing the file's
owner or group, write the file's numeric UID or GID rather
than the user or group name, respectively. Disable the −C,
−m, and −x options.
−o Turn on the −l (ell) option, but disable writing the file's
group name or number. Disable the −C, −m, and −x options.
−p Write a ('/') after each filename if that file is a
−q Force each instance of non-printable filename characters
and characters to be written as the
('?') character. Implementations may provide this option
by default if the output is to a terminal device.
−r Reverse the order of the sort to get reverse collating
sequence oldest first, or smallest file size first
depending on the other options given.
−s Indicate the total number of file system blocks consumed by
each file displayed. If the −k option is also specified,
the block size shall be 1024 bytes; otherwise, the block
size is implementation-defined.
−t Sort with the primary key being time modified (most
recently modified first) and the secondary key being
filename in the collating sequence. For a symbolic link,
the time used as the sort key is that of the symbolic link
itself, unless ls is evaluating its file information to be
that of the file referenced by the link (see the −H and −L
−u Use time of last access (see the Base Definitions volume of
POSIX.1‐2008, sys_stat.h(0p)) instead of last modification
of the file for sorting (−t) or writing (−l).
−x The same as −C, except that the multi-text-column output is
produced with entries sorted across, rather than down, the
columns. This option disables long format output.
−1 (The numeric digit one.) Force output to be one entry per
line. This option does not disable long format output.
(Long format output is enabled by −g, −l (ell), −n, and −o;
and disabled by −C, −m, and −x.)
If an option that enables long format output (−g, −l (ell), −n, and
−o is given with an option that disables long format output (−C, −m,
and −x), this shall not be considered an error. The last of these
options specified shall determine whether long format output is
If −R, −d, or −f are specified, the results of specifying these
mutually-exclusive options are specified by the descriptions of these
options above. If more than one of any of the other options shown in
the SYNOPSIS section in mutually-exclusive sets are given, this shall
not be considered an error; the last option specified in each set
shall determine the output.
Note that if −t is specified, −c and −u are not only mutually-
exclusive with each other, they are also mutually-exclusive with −S
when determining sort order. But even if −S is specified after all
occurrences of −c, −t, and −u, the last use of −c or −u determines
the timestamp printed when producing long format output.
The following operand shall be supported:
file A pathname of a file to be written. If the file specified
is not found, a diagnostic message shall be output on
INPUT FILES top
ENVIRONMENT VARIABLES top
The following environment variables shall affect the execution of ls:
COLUMNS Determine the user's preferred column position width for
writing multiple text-column output. If this variable
contains a string representing a decimal integer, the ls
utility shall calculate how many pathname text columns to
write (see −C) based on the width provided. If COLUMNS is
not set or invalid, an implementation-defined number of
column positions shall be assumed, based on the
implementation's knowledge of the output device. The column
width chosen to write the names of files in any given
directory shall be constant. Filenames shall not be
truncated to fit into the multiple text-column output.
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions
volume of POSIX.1‐2008, Section 8.2, Internationalization
Variables for the precedence of internationalization
variables used to determine the values of locale
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
Determine the locale for character collation information in
determining the pathname collation sequence.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte
as opposed to multi-byte characters in arguments) and which
characters are defined as printable (character class
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
LC_TIME Determine the format and contents for date and time strings
written by ls.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
TZ Determine the timezone for date and time strings written by
ls. If TZ is unset or null, an unspecified default
timezone shall be used.
ASYNCHRONOUS EVENTS top
The default format shall be to list one entry per line to standard
output; the exceptions are to terminals or when one of the −C, −m, or
−x options is specified. If the output is to a terminal, the format
When −m is specified, the format used for the last element of the
list shall be:
The format used for each other element of the list shall be:
where, if there is not room for the next element of the list to fit
within the current line length, is a string containing an
optional character and a mandatory character;
otherwise it is a single character.
If the −i option is specified, the file's file serial number (see the
Base Definitions volume of POSIX.1‐2008, sys_stat.h(0p)) shall be
written in the following format before any other output for the
If the −l option is specified, the following information shall be
written for files other than character special and block special
"%s %u %s %s %u %s %s\n", , ,
, , , ,
If the −l option is specified, the following information shall be
written for character special and block special files:
"%s %u %s %s %s %s %s\n", , ,
, , , ,
In both cases if the file is a symbolic link and the −L option is
also specified, this information shall be for the file resolved from
the symbolic link, except that the field shall contain the
pathname of the symbolic link itself. If the file is a symbolic link
and the −L option is not specified, this information shall be about
the link itself and the field shall be of the form:
"%s −> %s", ,
The −n, −g, and −o options use the same format as −l, but with
omitted items and their associated characters. See the
In both the preceding −l forms, if or
cannot be determined, or if −n is given, they shall be replaced with
their associated numeric values using the format %u.
The field shall contain the value that would be returned for
the file in the st_size field of struct stat (see the Base
Definitions volume of POSIX.1‐2008, sys_stat.h(0p)). Note that for
some file types this value is unspecified.
The field shall contain implementation-defined
information associated with the device in question.
The field shall contain the appropriate date and
timestamp of when the file was last modified. In the POSIX locale,
the field shall be the equivalent of the output of the following date
date "+%b %e %H:%M"
if the file has been modified in the last six months, or:
date "+%b %e %Y"
(where two characters are used between %e and %Y) if the file
has not been modified in the last six months or if the modification
date is in the future, except that, in both cases, the final
produced by date shall not be included and the output shall
be as if the date command were executed at the time of the last
modification date of the file rather than the current time. When the
LC_TIME locale category is not set to the POSIX locale, a different
format and order of presentation of this field may be used.
If the pathname was specified as a file operand, it shall be written
The file mode written under the −l, −n, −g, and −o options shall
consist of the following format:
"%c%s%s%s%s", , ,
The shall be the empty string
if there is no alternate or additional access control method
associated with the file; otherwise, it shall be a string containing
a single printable character that is not a .
The character shall describe the type of file, as
b Block special file.
c Character special file.
l (ell) Symbolic link.
− Regular file.
Implementations may add other characters to this list to represent
other implementation-defined file types.
The next three fields shall be three characters each:
Permissions for the file owner class (see the Base Definitions
volume of POSIX.1‐2008, Section 4.4, File Access Permissions).
Permissions for the file group class.
Permissions for the file other class.
Each field shall have three character positions:
1. If 'r', the file is readable; if '−', the file is not readable.
2. If 'w', the file is writable; if '−', the file is not writable.
3. The first of the following that applies:
S If in , the file is not executable and
set-user-ID mode is set. If in , the
file is not executable and set-group-ID mode is set.
s If in , the file is executable and set-
user-ID mode is set. If in , the file is
executable and set-group-ID mode is set.
T If in and the file is a directory,
search permission is not granted to others, and the
restricted deletion flag is set.
t If in and the file is a directory,
search permission is granted to others, and the restricted
deletion flag is set.
x The file is executable or the directory is searchable.
− None of the attributes of 'S', 's', 'T', 't', or 'x'
Implementations may add other characters to this list for the
third character position. Such additions shall, however, be
written in lowercase if the file is executable or searchable, and
in uppercase if it is not.
If any of the −l, −n, −s, −g, or −o options is specified, each list
of files within the directory shall be preceded by a status line
indicating the number of file system blocks occupied by files in the
directory in 512-byte units if the −k option is not specified, or
1024-byte units if the −k option is specified, rounded up to the next
integral number of units, if necessary. In the POSIX locale, the
format shall be:
If more than one directory, or a combination of non-directory files
and directories are written, either as a result of specifying
multiple operands, or the −R option, each list of files within a
directory shall be preceded by:
If this string is the first thing to be written, the first
shall not be written. This output shall precede the number of units
in the directory.
If the −s option is given, each file shall be written with the number
of blocks used by the file. Along with −C, −1, −m, or −x, the number
and a shall precede the filename; with −l, −n, −g, or −o,
they shall precede each line describing a file.
The standard error shall be used only for diagnostic messages.
OUTPUT FILES top
EXTENDED DESCRIPTION top
EXIT STATUS top
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS top
The following sections are informative.
APPLICATION USAGE top
Many implementations use the ('=') to denote sockets
bound to the file system for the −F option. Similarly, many
historical implementations use the 's' character to denote sockets as
the entry type characters for the −l option.
It is difficult for an application to use every part of the file
modes field of ls −l in a portable manner. Certain file types and
executable bits are not guaranteed to be exactly as shown, as
implementations may have extensions. Applications can use this field
to pass directly to a user printout or prompt, but actions based on
its contents should generally be deferred, instead, to the test
The output of ls (with the −l and related options) contains
information that logically could be used by utilities such as chmod
and touch to restore files to a known state. However, this
information is presented in a format that cannot be used directly by
those utilities or be easily translated into a format that can be
used. A character has been added to the end of the permissions string
so that applications at least have an indication that they may be
working in an area they do not understand instead of assuming that
they can translate the permissions string into something that can be
used. Future versions or related documents may define one or more
specific characters to be used based on different standard additional
or alternative access control mechanisms.
As with many of the utilities that deal with filenames, the output of
ls for multiple files or in one of the long listing formats must be
used carefully on systems where filenames can contain embedded white
space. Systems and system administrators should institute policies
and user training to limit the use of such filenames.
The number of disk blocks occupied by the file that it reports varies
depending on underlying file system type, block size units reported,
and the method of calculating the number of blocks. On some file
system types, the number is the actual number of blocks occupied by
the file (counting indirect blocks and ignoring holes in the file);
on others it is calculated based on the file size (usually making an
allowance for indirect blocks, but ignoring holes).
An example of a small directory tree being fully listed with ls
−laRF a in the POSIX locale:
drwxr-xr-x 3 fox prog 64 Jul 4 12:07 ./
drwxrwxrwx 4 fox prog 3264 Jul 4 12:09 ../
drwxr-xr-x 2 fox prog 48 Jul 4 12:07 b/
-rwxr--r-- 1 fox prog 572 Jul 4 12:07 foo*
drwxr-xr-x 2 fox prog 48 Jul 4 12:07 ./
drwxr-xr-x 3 fox prog 64 Jul 4 12:07 ../
-rw-r--r-- 1 fox prog 700 Jul 4 12:07 bar
Some historical implementations of the ls utility show all entries in
a directory except dot and dot-dot when a superuser invokes ls
without specifying the −a option. When ``normal'' users invoke ls
without specifying −a, they should not see information about any
files with names beginning with a unless they were named as
Implementations are expected to traverse arbitrary depths when
processing the −R option. The only limitation on depth should be
based on running out of physical storage for keeping track of
The −1 (one) option was historically found in BSD and BSD-derived
implementations only. It is required in this volume of POSIX.1‐2008
so that conforming applications might ensure that output is one entry
per line, even if the output is to a terminal.
The −S option was added in Issue 7, but had been provided by several
implementations for many years. The description given in the standard
documents historic practice, but does not match much of the
documentation that described its behavior. Historical documentation
typically described it as something like:
−S Sort by size (largest size first) instead of by name.
Special character devices (listed last) are sorted by name.
even though the file type was never considered when sorting the
output. Character special files do typically sort close to the end
of the list because their file size on most implementations is zero.
But they are sorted alphabetically with any other files that happen
to have the same file size (zero), not sorted separately and added to
This volume of POSIX.1‐2008 is frequently silent about what happens
when mutually-exclusive options are specified. Except for −R, −d, and
−f, the ls utility is required to accept multiple options from each
mutually-exclusive option set without treating them as errors and to
use the behavior specified by the last option given in each mutually-
exclusive set. Since ls is one of the most aliased commands, it is
important that the implementation perform intuitively. For example,
if the alias were:
alias ls="ls −C"
and the user typed ls −1 (one), single-text-column output should
result, not an error.
The −g, −l (ell), −n, and −o options are not mutually-exclusive
options. They all enable long format output. They work together to
determine whether the file's owner is written (no if −g is present),
file's group is written (no if −o is present), and if the file's
group or owner is written whether it is written as the name (default)
or a string representation of the UID or GID number (if −n is
present). The −C, −m, −x, and −1 (one) are mutually-exclusive options
and the first three of these disable long format output. The −1 (one)
option does not directly change whether or not long format output is
enabled, but by overriding −C, −m, and −x, it can re-enable long
format output that had been disabled by one of these options.
Earlier versions of this standard did not describe the BSD −A option
(like −a, but dot and dot-dot are not written out). It has been added
due to widespread implementation.
Implementations may make −q the default for terminals to prevent
trojan horse attacks on terminals with special escape sequences.
This is not required because:
* Some control characters may be useful on some terminals; for
example, a system might write them as "\001" or "^A".
* Special behavior for terminals is not relevant to applications
An early proposal specified that the had to be '+' if there was an
alternate access method used on the file or if there was not.
This was changed to be if there is not and a single printable
character if there is. This was done for three reasons:
1. There are historical implementations using characters other than
2. There are implementations that vary this character used in that
position to distinguish between various alternate access methods
3. The standard developers did not want to preclude future
specifications that might need a way to specify more than one
alternate access method.
Nonetheless, implementations providing a single alternate access
method are encouraged to use '+'.
Earlier versions of this standard did not have the −k option, which
meant that the −s option could not be used portably as its block size
was implementation-defined, and the units used to specify the number
of blocks occupied by files in a directory in an ls −l listing were
fixed as 512-byte units. The −k option has been added to provide a
way for the −s option to be used portably, and for consistency it
also changes the aforementioned units from 512-byte to 1024-byte.
The field in the −l format is specified only for the
POSIX locale. As noted, the format can be different in other locales.
No mechanism for defining this is present in this volume of
POSIX.1‐2008, as the appropriate vehicle is a messaging system; that
is, the format should be specified as a ``message''.
FUTURE DIRECTIONS top
Allowing −f to ignore the −A, −g, −l, −n, −o, and −s options may be
removed in a future version.
SEE ALSO top
The Base Definitions volume of POSIX.1‐2008, Section 4.4, File Access
Permissions, Chapter 8, Environment Variables, Section 12.2, Utility
Syntax Guidelines, sys_stat.h(0p)
The System Interfaces volume of POSIX.1‐2008, fstatat(3p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
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