"GNU CoreUtils 9.1说明文档：GNU核心工具和标准程序手册"

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GNU Coreutils 9.1是GNU核心工具的最新版本，提供了一套标准程序用于文本和文件处理。该软件的最新版本为9.1，于2022年4月15日发布。本手册由David MacKenzie等人编写，版权所有1994年至2022年归自由软件基金会所有。根据GNU自由文档许可证的条款，允许复制、分发和/或修改本文档，无论是版本1.3还是由自由软件基金会发布的任何以后版本，都不得有不变的章节或前置条件。 GNU Coreutils是一个功能强大的工具集合，用于在GNU/Linux和其他类Unix系统上进行常见的文本和文件操作。这些工具包括但不限于文件管理、文本处理、shell脚本编程、系统管理等。从文件和目录的操作到文本流的处理，GNU Coreutils为用户提供了强大的工具，以提高他们在这些系统上的工作效率。 GNU Coreutils 9.1的说明文档详细介绍了每个工具的使用方法、选项和参数，并提供了大量的示例和用法说明。用户可以从中学习如何使用这些工具来完成各种常见的任务，如复制、移动、重命名文件，以及对文本进行搜索、替换、排序等操作。同时，说明文档还介绍了如何将这些工具结合起来，编写复杂的文本处理管道和脚本，以满足用户需求。在GNU Coreutils 9.1中，还包含了一些新的工具和功能，以及对现有工具的改进和优化。这些更新不仅提高了工具集的功能和性能，还使得用户可以更加方便地进行文本和文件处理工作。通过说明文档，用户可以快速了解这些新功能的使用方法和优势，以便更好地利用它们。总之，GNU Coreutils 9.1说明文档是GNU核心工具集的完整参考手册，为用户提供了使用这些工具的详细指南和示例。无论是初学者还是有经验的用户，都可以通过这份文档快速掌握这些工具的使用方法，从而提高其在GNU/Linux和其他类Unix系统上的工作效率。同时，说明文档还为用户提供了了解最新功能和改进的途径，以便及时更新其工作流程和技术栈。通过不断地学习和掌握这些工具，用户可以更好地应对各种文本和文件处理需求，从而更加高效地完成其工作。 GNU Coreutils 9.1是GNU核心工具的最新版本，提供了一套标准程序用于文本和文件处理。该软件的最新版本为9.1，于2022年4月15日发布。本手册由David MacKenzie等人编写，版权所有1994年至2022年归自由软件基金会所有。根据GNU自由文档许可证的条款，允许复制、分发和/或修改本文档，无论是版本1.3还是由自由软件基金会发布的任何以后版本，都不得有不变的章节或前置条件。 GNU Coreutils是一个功能强大的工具集合，用于在GNU/Linux和其他类Unix系统上进行常见的文本和文件操作。这些工具包括但不限于文件管理、文本处理、shell脚本编程、系统管理等。从文件和目录的操作到文本流的处理，GNU Coreutils为用户提供了强大的工具，以提高他们在这些系统上的工作效率。 GNU Coreutils 9.1的说明文档详细介绍了每个工具的使用方法、选项和参数，并提供了大量的示例和用法说明。用户可以从中学习如何使用这些工具来完成各种常见的任务，如复制、移动、重命名文件，以及对文本进行搜索、替换、排序等操作。同时，说明文档还介绍了如何将这些工具结合起来，编写复杂的文本处理管道和脚本，以满足用户需求。在GNU Coreutils 9.1中，还包含了一些新的工具和功能，以及对现有工具的改进和优化。这些更新不仅提高了工具集的功能和性能，还使得用户可以更加方便地进行文本和文件处理工作。通过说明文档，用户可以快速了解这些新功能的使用方法和优势，以便更好地利用它们。总之，GNU Coreutils 9.1说明文档是GNU核心工具集的完整参考手册，为用户提供了使用这些工具的详细指南和示例。无论是初学者还是有经验的用户，都可以通过这份文档快速掌握这些工具的使用方法，从而提高其在GNU/Linux和其他类Unix系统上的工作效率。同时，说明文档还为用户提供了了解最新功能和改进的途径，以便及时更新其工作流程和技术栈。通过不断地学习和掌握这些工具，用户可以更好地应对各种文本和文件处理需求，从而更加高效地完成其工作。

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Chapter 2: Common options 6

These ﬂoating point numbers therefore can use scientiﬁc notation like 1.0e-34 and -10e100.

Commands that parse ﬂoating point also understand case-insensitive inf, infinity, and

NaN, although whether such values are useful depends on the command in question. Modern

C implementations also accept hexadecimal ﬂoating point numbers such as -0x.ep-3, which

stands for −14/16 times 2

−

3, which equals −0.109375. See Section “Parsing of Floats” in

The GNU C Library Reference Manual.

Normally the LC_NUMERIC locale determines the decimal-point character. However, some

commands’ descriptions specify that they accept numbers in either the current or the C

locale; for example, they treat ‘3.14’ like ‘3,14’ if the current locale uses comma as a

decimal point.

2.5 Signal speciﬁcations

A signal may be a signal name like ‘HUP’, or a signal number like ‘1’, or an exit status of a

process terminated by the signal. A signal name can be given in canonical form or preﬁxed

by ‘SIG’. The case of the letters is ignored. The following signal names and numbers are

supported on all POSIX compliant systems:

‘HUP’ 1. Hangup.

‘INT’ 2. Terminal interrupt.

‘QUIT’ 3. Terminal quit.

‘ABRT’ 6. Process abort.

‘KILL’ 9. Kill (cannot be caught or ignored).

‘ALRM’ 14. Alarm Clock.

‘TERM’ 15. Termination.

Other supported signal names have system-dependent corresponding numbers. All systems

conforming to POSIX 1003.1-2001 also support the following signals:

‘BUS’ Access to an undeﬁned portion of a memory object.

‘CHLD’ Child process terminated, stopped, or continued.

‘CONT’ Continue executing, if stopped.

‘FPE’ Erroneous arithmetic operation.

‘ILL’ Illegal Instruction.

‘PIPE’ Write on a pipe with no one to read it.

‘SEGV’ Invalid memory reference.

‘STOP’ Stop executing (cannot be caught or ignored).

‘TSTP’ Terminal stop.

‘TTIN’ Background process attempting read.

‘TTOU’ Background process attempting write.

‘URG’ High bandwidth data is available at a socket.

Chapter 2: Common options 8

2.7 Sources of random data

The shuf, shred, and sort commands sometimes need random data to do their work. For

example, ‘sort -R’ must choose a hash function at random, and it needs random data to

make this selection.

By default these commands use an internal pseudo-random generator initialized by

a small amount of entropy, but can be directed to use an external source with the

--random-source=file option. An error is reported if ﬁle does not contain enough bytes.

For example, the device ﬁle /dev/urandom could be used as the source of random data.

Typically, this device gathers environmental noise from device drivers and other sources

into an entropy pool, and uses the pool to generate random bits. If the pool is short of

data, the device reuses the internal pool to produce more bits, using a cryptographically

secure pseudo-random number generator. But be aware that this device is not designed for

bulk random data generation and is relatively slow.

/dev/urandom suﬃces for most practical uses, but applications requiring high-value or

long-term protection of private data may require an alternate data source like /dev/random

or /dev/arandom. The set of available sources depends on your operating system.

To reproduce the results of an earlier invocation of a command, you can save some

random data into a ﬁle and then use that ﬁle as the random source in earlier and later invo-

cations of the command. Rather than depending on a ﬁle, one can generate a reproducible

arbitrary amount of pseudo-random data given a seed value, using for example:

get_seeded_random()

{

seed="$1"

openssl enc -aes-256-ctr -pass pass:"$seed" -nosalt \

</dev/zero 2>/dev/null

}

shuf -i1-100 --random-source=<(get_seeded_random 42)

2.8 Target directory

The cp, install, ln, and mv commands normally treat the last operand specially when it

is a directory or a symbolic link to a directory. For example, ‘cp source dest’ is equivalent

to ‘cp source dest/source’ if dest is a directory. Sometimes this behavior is not exactly

what is wanted, so these commands support the following options to allow more ﬁne-grained

control:

‘-T’

‘--no-target-directory’

Do not treat the last operand specially when it is a directory or a symbolic link

to a directory. This can help avoid race conditions in programs that operate in

a shared area. For example, when the command ‘mv /tmp/source /tmp/dest’

succeeds, there is no guarantee that /tmp/source was renamed to /tmp/dest:

it could have been renamed to /tmp/dest/source instead, if some other process

created /tmp/dest as a directory. However, if mv -T /tmp/source /tmp/dest

succeeds, there is no question that /tmp/source was renamed to /tmp/dest.

Chapter 2: Common options 9

In the opposite situation, where you want the last operand to be treated as a di-

rectory and want a diagnostic otherwise, you can use the --target-directory

(-t) option.

‘-t directory’

‘--target-directory=directory’

Use directory as the directory component of each destination ﬁle name.

The interface for most programs is that after processing options and a ﬁnite

(possibly zero) number of ﬁxed-position arguments, the remaining argument

list is either expected to be empty, or is a list of items (usually ﬁles) that will

all be handled identically. The xargs program is designed to work well with

this convention.

The commands in the mv-family are unusual in that they take a variable number

of arguments with a special case at the end (namely, the target directory). This

makes it nontrivial to perform some operations, e.g., “move all ﬁles from here

to ../d/”, because mv * ../d/ might exhaust the argument space, and ls |

xargs ... doesn’t have a clean way to specify an extra ﬁnal argument for each

invocation of the subject command. (It can be done by going through a shell

command, but that requires more human labor and brain power than it should.)

The --target-directory (-t) option allows the cp, install, ln, and mv pro-

grams to be used conveniently with xargs. For example, you can move the ﬁles

from the current directory to a sibling directory, d like this:

ls | xargs mv -t ../d --

However, this doesn’t move ﬁles whose names begin with ‘.’. If you use the

GNU find program, you can move those ﬁles too, with this command:

find . -mindepth 1 -maxdepth 1 \

| xargs mv -t ../d

But both of the above approaches fail if there are no ﬁles in the current directory,

or if any ﬁle has a name containing a blank or some other special characters.

The following example removes those limitations and requires both GNU find

and GNU xargs:

find . -mindepth 1 -maxdepth 1 -print0 \

| xargs --null --no-run-if-empty \

mv -t ../d

The --target-directory (-t) and --no-target-directory (-T) options cannot be com-

bined.

2.9 Trailing slashes

Some GNU programs (at least cp and mv) allow you to remove any trailing slashes from each

source argument before operating on it. The --strip-trailing-slashes option enables

this behavior.

This is useful when a source argument may have a trailing slash and specify a symbolic

link to a directory. This scenario is in fact rather common because some shells can automat-

ically append a trailing slash when performing ﬁle name completion on such symbolic links.

Chapter 2: Common options 10

Without this option, mv, for example, (via the system’s rename function) must interpret a

trailing slash as a request to dereference the symbolic link and so must rename the indirectly

referenced directory and not the symbolic link. Although it may seem surprising that such

behavior be the default, it is required by POSIX and is consistent with other parts of that

standard.

2.10 Traversing symlinks

The following options modify how chown and chgrp traverse a hierarchy when the

--recursive (-R) option is also speciﬁed. If more than one of the following options is

speciﬁed, only the ﬁnal one takes eﬀect. These options specify whether processing a

symbolic link to a directory entails operating on just the symbolic link or on all ﬁles in the

hierarchy rooted at that directory.

These options are independent of --dereference and --no-dereference (-h), which

control whether to modify a symlink or its referent.

‘-H’ If --recursive (-R) is speciﬁed and a command line argument is a symbolic

link to a directory, traverse it.

‘-L’ In a recursive traversal, traverse every symbolic link to a directory that is

encountered.

‘-P’ Do not traverse any symbolic links. This is the default if none of -H, -L, or -P

is speciﬁed.

2.11 Treating / specially

Certain commands can operate destructively on entire hierarchies. For example, if a user

with appropriate privileges mistakenly runs ‘rm -rf / tmp/junk’, that may remove all ﬁles

on the entire system. Since there are so few legitimate uses for such a command, GNU rm

normally declines to operate on any directory that resolves to /. If you really want to try

to remove all the ﬁles on your system, you can use the --no-preserve-root option, but

the default behavior, speciﬁed by the --preserve-root option, is safer for most purposes.

The commands chgrp, chmod and chown can also operate destructively on entire hier-

archies, so they too support these options. Although, unlike rm, they don’t actually unlink

ﬁles, these commands are arguably more dangerous when operating recursively on /, since

they often work much more quickly, and hence damage more ﬁles before an alert user can

interrupt them. Tradition and POSIX require these commands to operate recursively on

/, so they default to --no-preserve-root, but using the --preserve-root option makes

them safer for most purposes. For convenience you can specify --preserve-root in an

alias or in a shell function.

Note that the --preserve-root option also ensures that chgrp and chown do not modify

/ even when dereferencing a symlink pointing to /.

2.12 Special built-in utilities

Some programs like nice can invoke other programs; for example, the command ‘nice cat

file’ invokes the program cat by executing the command ‘cat file’. However, special

built-in utilities like exit cannot be invoked this way. For example, the command ‘nice

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