Questions tagged [coreutils]

GNU Core Utilities are the GNU project's implementation of the core command-line tools of a POSIX system, including tools like ls, cp, mv, rm, etc.

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227
votes
3answers
46k views

Why is 'ls' suddenly wrapping items with spaces in single quotes?

I just noticed that on one of my machines (running Debian Sid) whenever I type ls any file name with spaces has single quotes surrounding it. I immediately checked my aliases, only to find them intact....
71
votes
13answers
65k views

Correct locking in shell scripts?

Sometimes you have to make sure that only one instance of a shell script is running at the same time. For example a cron job which is executed via crond that does not provide locking on its own (e.g. ...
61
votes
3answers
9k views

How does `yes` write to file so quickly?

Let me give an example: $ timeout 1 yes "GNU" > file1 $ wc -l file1 11504640 file1 $ for ((sec0=`date +%S`;sec<=$(($sec0+5));sec=`date +%S`)); do echo "GNU" >> file2; done $ wc -l file2 ...
58
votes
2answers
123k views

cp -L vs. cp -H

Problem When copying files with cp -H or cp -L, I get the same results: $ ls -l fileA fileA -> fileB $ cp fileA somewhere/ -H $ ls -l somewhere/ fileA # fileA is a copy of fileB, only ...
54
votes
5answers
13k views

Why is cp --reflink=auto not the default behaviour?

Why is cp --reflink=auto not the default behaviour? Could it cause any harm to enable it? Is it possible to enable it at compile time, so it is used all across the system, not just in interactive ...
32
votes
3answers
3k views

What is the `[` program that resides in my system's /bin?

I was recently browsing my Fedora's /bin folder and noticed a binary named [. I did try to search the internet for more information on that, but I couldn't find anything useful. Running it through ...
30
votes
4answers
137k views

Storing output of command in shell variable [duplicate]

I have an operation using cut that I would like to assign result to a variable var4=echo ztemp.xml |cut -f1 -d '.' I get the error: ztemp.xml is not a command The value of var4 never gets ...
30
votes
2answers
2k views

Why does ln -s accept a single argument

> cd /tmp > ln -s foo > ls -alhF /tmp lrwxrwxrwx 1 user user 3 Jul 29 14:00 foo -> foo Is this a bug in ln or is there a use case for symlinking a file to itself? This is with ...
30
votes
3answers
30k views

GNU "install" -d flag -- how's it work?

I'm trying to write a makefile rule to copy a directory, maintaining its structure, and since all the other rules in our makefiles use install, I wanted to be consistent. In the manpage, it says: ...
29
votes
3answers
63k views

How does the "1 month ago" option in date command work?

I'm not sure if this gets the past date within the current day or if it only takes 30 or 31 days to it. e.g. If the current date is March 28th, 1 month ago must be February 28th, but what happen ...
26
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4answers
3k views

What is the added value of the -T option in GNU cp and mv?

Why do some GNU Coreutils commands have the -T/--no-target-directory option? It seems like everything that it does can be achieved using the semantics of the . (self dot) in a traditional Unix ...
25
votes
3answers
36k views

Mac OS X: dircolors not found?

I just switched to a Macbook Air. I installed zsh using homebrew, but when I use some of the code that I (originally had) in my .zshrc, I get an error saying that .dircolors was not found. Below is ...
25
votes
6answers
19k views

Any options to replace GNU coreutils on Linux?

I've been thinking about discontinuing the use of GNU Coreutils on my Linux systems, but to be honest, unlike many other GNU components, I can't think of any alternatives (on Linux). What alternatives ...
24
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4answers
3k views

What is the use of the -f option for `touch`?

From man touch: -f (ignored) But I don't get what is meant by ignored. I've tried following: $ ls -l file -rw-rw-r-- 1 pandya pandya 0 Mar 20 16:17 file $ touch -f file $ ls -l file -rw-rw-r--...
24
votes
5answers
3k views

/usr/bin/ptx: Can you provide a use case or two?

I was going through the list of files included in coreutils and I was able to come up with an example of how I could personally use all of the commands provided except for ptx. Can you give one or two ...
24
votes
3answers
28k views

Problem with install command to copy a whole directory

So I have a repo with some of my config files and I'm trying to create a makefile to install them in the homedir. The problem I have is that when I run the following command straight in bash install -...
23
votes
3answers
5k views

Why is cp's option not to overwrite files called --no-clobber?

cp is a massively popular Linux tool maintained by the coreutils team of the GNU foundation. By default, files with the same name will be overwritten, if the user wants to change this behaviour they ...
23
votes
6answers
5k views

Is there a practical use for the GNU factor command?

Looking through the GNU Coreutils, I spotted the factor command, that I had never noticed before. Reading the man page: Print the prime factors of each specified integer NUMBER. If none are ...
22
votes
2answers
2k views

md5sum prepends '\' to the checksum

Why md5sum is prepending "\" in front of the checksum when finding the checksum of a file with "\" in the name? $ md5sum /tmp/test\\test \d41d8cd98f00b204e9800998ecf8427e /tmp/test\\test The same ...
22
votes
3answers
4k views

Why is coreutils sort slower than Python?

I wrote the following script to test the speed of Python's sort functionality: from sys import stdin, stdout lines = list(stdin) lines.sort() stdout.writelines(lines) I then compared this to the ...
20
votes
2answers
8k views

How is the order in which tar works on files determined?

$ touch dir/{{1..8},{a..p}} $ tar cJvf file.tar.xz dir/ dir/ dir/o dir/k dir/b dir/3 dir/1 dir/i dir/7 dir/4 dir/e dir/a dir/g dir/2 dir/d dir/5 dir/8 dir/c dir/n dir/f dir/h dir/6 dir/l dir/m dir/j ...
20
votes
3answers
23k views

How can I display octal notation of permissions with ls - and can octal represent all permissions? [duplicate]

After looking at the man page for ls on my system and searching Google, I see there IS a hack of way to use awk or perl to show octal permissions when using ls, but with bash is there anything more ...
19
votes
3answers
30k views

What's the real point of the -f option on rm?

By reading the GNU coreutils man page for rm, one of the options is -f, which according to the manual, -f, --force ignore nonexistent files and arguments, never prompt Now, I made some ...
18
votes
2answers
2k views

coreutils that are utf aware?

When I used cut today, I found out it doesn't treat a UTF-8 character as a character, but 3 characters because it's 3 bytes long. This seems to be generally true for many tools. Are there versions ...
17
votes
2answers
5k views

`set -e` and `grep` idiom for preventing premature exit from shell script when pattern not found

Help required - in the context of shell scripting on a GNU/LINUX bash: I always use set -e. Often, I would like to grep and do not always want the script to terminate execution if grep has an exit ...
16
votes
2answers
5k views

`tee` for commands

tee can redirect the piped standard input into the standard output and file. echo Hello, World! | tee greeting.txt The command above would display the greeting on the terminal screen and save it in ...
16
votes
4answers
8k views

sort by hex value

Using coreutils sort, how can I sort numerically by a hexadecimal value (field)? I was expecting something along the lines of sort -k3,3x file_to_sort however, such an x does not exist. Edit: Best ...
15
votes
5answers
3k views

How to run a command 1 out of N times in Bash

I want a way to run a command randomly, say 1 out of 10 times. Is there a builtin or GNU coreutil to do this, ideally something like: chance 10 && do_stuff where do_stuff is only executed 1 ...
15
votes
2answers
726 views

`test` and `[` - different binaries, any difference?

I noticed while answering another question that test and [ are different binaries, but the [ manpage pulls up test's. Besides the requirement for an ending ], is there any difference? If not, why are ...
14
votes
1answer
19k views

Behavior of `du` command with `-L` flag

I've noticed a strange behavior with du command when it's used with -L command line option. I'm using Slackware 14 and Coreutils 8.19. To reproduce the strange behavior, create two folders: mkdir ...
13
votes
3answers
23k views

cp --no-target-directory explained

Question: I need a simple example of how to use cp --no-target-directory. I do experience some difficulties in understanding cp --no-target-directory. I do understand the explanation for mv --no-...
13
votes
2answers
4k views

`du -s .` and `du -hs .` gives different results (on OS X)

The difference with and without -h should only be the human readable units, right? Well apparently no... $ du -s . 74216696 . $ du -hs . 35G . Or maybe I'm mistaken and the result of du -s . ...
12
votes
2answers
984 views

Explanation of tac --before

-b, --before The separator is attached to the beginning of the record that it precedes in the file. And I can't understand the following output: $ echo -e "Hello\nNew\nWorld\n!" > file $ ...
12
votes
1answer
6k views

Are there any disadvantages of `cp --sparse=always`?

Is there any reason not to use use --sparse=always with every invocation to cp? info cp says: ‘--sparse=WHEN’ A “sparse file” contains “holes”—a sequence of zero bytes that does not occupy ...
11
votes
5answers
35k views

Why can't mv deal with existence of same-name directory in destination?

mv can't move a directory to a destination with a same-name directory: $ mv fortran/ imperative_PLs/ mv: cannot move ‘fortran/’ to ‘imperative_PLs/fortran’: Directory not empty Why does mv not work ...
11
votes
1answer
274 views

Is there a way to express: `--link` or fall back to ordinary copy in cp (from GNU coreutils)?

Is there a way to tell cp to --link (i.e. create hard links), but fall back in the case where I am attempting inter-device hardlinks? Inter-device links aren't possible and would cause cp to fail. ...
11
votes
1answer
62k views

Command to transpose (swap rows and columns of) a text file [duplicate]

Is there currently a generic command that will "pivot" input. e.g. #labeled.file name: bob title: code monkey name: joe title: pointy haired is converted to: name title bob code monkey joe ...
10
votes
1answer
1k views

'sort' produces output in a weird order

Consider the following input to sort: cat > foo <<EOM D,,5014978 DD,,25 D,I,1972765530 D,Y,4223624 -,Y,71285059 YA,I,2 EOM Now try running sort foo. The output is not sorted when trying this ...
10
votes
4answers
904 views

Which version of X introduced feature Y?

A big part of my daily job is developing software for use on machines with different versions of the same software, like bash, find, and grep. When encountering a feature which would be useful for ...
10
votes
4answers
9k views

Make cp return an error value if the target exists

Is there a way to make cp (from GNU coreutils on Linux) return a nonzero value in case the target file does already exist? Or is there any other small utility which is commonly available and which ...
9
votes
2answers
1k views

What languages are used to build Unix commands?

Examples of commands I'm referring to are ls, pwd, and cd. Also, how are these built? Do you have an example?
9
votes
2answers
2k views

What is the point of ls -f (or, why is this hanging?)

I've got a directory with about 100,000 files in it. ls -f hangs for over a minute. I ran strace, and immediately started seeing getdents, so ls is clearly reading the directory. I also see a lot ...
9
votes
2answers
3k views

Trailing slashes on symbolic links to directories

I'm trying to emulate the process of path resolution (see man page path_resolution) in unix-like systems. My OS is Linux with GNU coreutils 8.7. In order to clarify the meaning of extra trailing '/' ...
8
votes
5answers
681 views

How intelligent are unix utilities?

Unix utilities like sort, find, grep, diff et al are very handy to perform quick tasks, sometimes without writing any code at all. I wanted to know what algorithms do they internally use and how do ...
8
votes
2answers
2k views

How to find a partial directory path?

Suppose I don't know where my Django source is stored, but I know that it contains these directories in this way: django/contrib/admin. How can I use the find command or any more appropriate ...
8
votes
3answers
3k views

How to find out if a file on btrfs is copy-on-write?

I know that cp has a --reflink option to control full copies vs. copy-on-write "copies". On btrfs, can I use ls (or some other command) to find out whether a file shares (in a copy-on-write senses) ...
7
votes
4answers
2k views

What's the safest, most portable way to invoke the echo binary?

The echo in coreutils seems to be ubiquitous, but not every system will have it in the same place (usually /bin/echo). What's the safest way to invoke this echo without knowing where it is? I'm ...
7
votes
6answers
42k views

ls command - define number of columns

Is there a way to define the number of columns in ls output? I got this far: ls -C sorts in columns and ls -1 produces one column. --tabsize = option to produce two columns resulted in what looks ...
7
votes
2answers
5k views

shuf file --output file: in-place shuffling

The shuf command has an --output flag that you can use to specify where to write its output (instead of writing to stdout). I want to shuffle a file in-place. Is it safe to use shuf file --output ...
7
votes
1answer
3k views

How do I interpret the output of dd when the option status=progress is chosen?

The dd manual page is very limited on this: ` status=LEVEL The LEVEL of information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' ...

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