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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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 ...
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11answers
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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. ...
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2answers
330 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 ...
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1answer
751 views

Is gnu coreutils sort broken?

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 ...
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3answers
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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 ...
13
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3answers
973 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 ...
4
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2answers
564 views

tac command's option creates strange output [comprehension question]

Say I have this file, containing nothing but a b c b a Using tac --separator=a file in BASH [on a Debian based Linux], I get this: # empty line # empty line b c ...
41
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3answers
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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 ...
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3answers
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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 ...
11
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3answers
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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 ...
9
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3answers
605 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 ...
4
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2answers
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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) ...
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4answers
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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 ...
8
votes
2answers
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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 ...
5
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3answers
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convert soft- to hardlinks with cp

The cp command's infopage offers on the option --preserve= the following: links Preserve in the destination files any links between corresponding source files. Note that with -L' ...
5
votes
2answers
2k 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 '/' ...
4
votes
1answer
119 views

mv overwrites read-only file without prompting

The GNU Coreutils manual for mv says: If a destination file exists but is normally unwritable, standard input is a terminal, and the -f or --force option is not given, mv prompts the user for ...
5
votes
1answer
162 views

Is there a command line tool to manage unix signals?

Is there a command runner like env, nice, nohup, etc., that can run a program with modified signals? In my case, I need something to reset SIGINT to SIG_DFL. Why do I need this? Because ...