Questions tagged [utilities]

small programs used on the command line to do a specific job

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588
votes
5answers
214k views

What does “--” (double-dash) mean?

I have seen -- used in the compgen command. For example: compgen -W "foo bar baz" -- b What is the meaning of the -- in there?
311
votes
16answers
405k views

How can I use sed to replace a multi-line string?

I've noticed that, if I add \n to a pattern for substituting using sed, it does not match. Example: $ cat > alpha.txt This is a test Please do not be alarmed $ sed -i'.original' 's/a test\nPlease ...
49
votes
7answers
10k views

How to trick a command into thinking its output is going to a terminal

Given a command that changes its behaviour when its output is going to a terminal (e.g. produce coloured output), how can that output be redirected in a pipeline while preserving the changed behaviour?...
89
votes
11answers
24k views

Linux tools to treat files as sets and perform set operations on them

Does anyone know of any linux tool specifically designed to treat files as sets and perform set operations on them? Like difference, intersection, etc?
75
votes
4answers
24k views

What is the difference between a builtin command and one that is not?

Is there any intrinsic difference between a builtin command and another command which can nominally do the same thing? eg. Do builtins get "special" treatement? ... is there less overhead running ...
121
votes
18answers
53k views

A standard tool to convert a byte-count into human KiB MiB etc; like du, ls1

Is there a standard tool which converts an integer count of Bytes into a human-readable count of the largest possible unit-size, while keeping the numeric value between 1.00 and 1023.99 ? I have my ...
137
votes
6answers
312k views

Usage of dash (-) in place of a filename

For a command, if using - as an argument in place of a file name will mean STDIN or STDOUT. But in this example, it creates a file with the name -: echo hello > - How can I make - in this ...
7
votes
1answer
2k views

Why is the rename utility on Debian/Ubuntu different than the one on other distributions, like CentOS?

On CentOS, the rename command uses two simple strings, from and to. rename from to file... while on Debian/Ubuntu it uses a perl-style regular expression. rename [ -v ] [ -n ] [ -f ] perlexpr [ ...
30
votes
4answers
6k views

Can a file that was originally sparse and then expanded be made sparse again?

I know that copying or transferring what was originally a sparse file without using a utility that understands sparse files will cause the 'holes' to be filled out. Is there a method or utility to ...
24
votes
11answers
21k views

Tool in UNIX to subtract dates

Is there any tool in Solaris UNIX (so no GNU tool available) to subtract dates? I know that in Linux we have gawk that can subtract one date from another. But in Solaris the maximum we have is nawk (...
9
votes
3answers
19k views

file block size - difference between stat and ls

I've noticed that when I do a: ls -ls file It provides block count, say 8 blocks. When I do: stat file I notice that the block count is 16, twice the number given by ls. The block size on my ...
95
votes
10answers
119k views

Is there any option with 'ls' command that I see only the directories?

Sometimes, I need to check only the directories not files. Is there any option with the command ls? Or is there any utility for doing that? EDIT: I'm using Mac OS X, and ls -d gives me . even though ...
88
votes
3answers
53k views

What is the point of the `yes` command? [duplicate]

This question concerns the yes command found in UNIX and Linux machines: Basically, what is the point (if any) and history of this tool? Are there practical applications for it? Can an example be ...
23
votes
5answers
103k views

How to recover data from a bad SD card?

I have a 4GB SD card with some family pictures on it that I need to recover. When I insert the card into my card reader, it shows up as an unknown 32MB device (as /dev/sde) and cannot be mounted. When ...
14
votes
2answers
638 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 ...
21
votes
3answers
4k views

Universal extractors

With an increasing number of archive/compression file formats, is there a single free/open-source command line tool to rule them all? Perhaps something with a consistent / unified set of flags? (note ...
13
votes
1answer
6k views

`unbuffer` or `stdbuf` for removing stdout buffering?

Is there a difference between unbuffer(1) and stdbuf(1)? From what I gather, unbuffer makes more than the "best effort" of calling the libc function set(X)buf at the beginning, and then letting things ...
23
votes
4answers
2k views

Are Linux utilities smart when running piped commands?

I was just running a few commands in a terminal and I started wondering, does Unix/Linux take shortcuts when running piped commands? For example, let's say I have a file with one million lines, the ...
4
votes
3answers
1k views

General specification for command line interface

I was wondering where I can find and learn some general idea about the command line interface used in Linux and bash? As to now, I have found pieces of such information only from experience, such as ...
9
votes
3answers
3k views

tr analog for unicode characters?

I need internationalized utility that does the same thing as tr: gets character from stream and substitutes it with a corresponding character. Not a particular case solution like lower-to-upper, but a ...
148
votes
3answers
671k views

How to list disks, partitions and filesystems in Linux? [duplicate]

In Windows, if you type LIST DISK using DiskPart in a command prompt it lists all physical storage devices, plus their size, format, etc. What is the equivalent of this in Linux?
74
votes
4answers
15k views

Why use install rather than cp and mkdir?

I've seen in many places used install -d to create directories and install -c to copy a file. Why not use mkdir and cp? Is there an advantage in using install?
5
votes
5answers
37k views

Where is the log of used commands in Linux?

In Linux, generally we use a lot of commands and it is difficult to remember all of them. history command provides the list of commands we used previously but its limit is less. New commands are ...
3
votes
3answers
4k views

ASCII art generator

I'm looking for an ASCII art generator (text is preferred, but images will do too) in the sl style, but with text instead of trains. Any suggestion?
83
votes
4answers
31k views

Fix or alternative for mktemp in OS X

I'm looking at a bash script someone else wrote that uses mktemp: TEMP=`mktemp --directory` However, this line does not work on my machine (OS X 10.6). How would I fix this line so that it is cross-...
31
votes
5answers
31k views

Setting the window dimensions of a running application

I'm trying to start an application within Ubuntu (xfce or gnome) and via the command line and was wondering if there's a generic way to set the dimensions of a given window of a given app that is ...
27
votes
4answers
64k views

touch: cannot touch file: No such file or directory [duplicate]

I am getting the error: touch: cannot touch `/opt/tsrm/compliance/cme/log/20121207.log`: No such file or directory on the touch command: touch $LOGFILE I also checked the link: touch: cannot touch ...
28
votes
3answers
7k views

What is the purpose of square bracket executable

I see there is an executable called "[" in /usr/bin. What is its purpose?
16
votes
4answers
4k views

Store output of a command into a ring-buffer

I've got a long-running command that generates a lot of output on stdout. I'd like to be able to retain, for instance, only the last three days or the last gibibyte (avoiding cutting lines in the ...
13
votes
3answers
1k views

Is there a way to make perl -i not clobber symlinks?

A friend of mine points out that if you do: perl -pi.bak -e 's/foo/bar/' somefile when "somefile" is actually a symlink, perl does just what the docs say it will do: It does this by renaming the ...
0
votes
4answers
2k views

Interactive cd (directory browser)

Sometimes when working in deeply nested file hierarchies (e.g. Java code) I find it annoying to traverse from one leaf to another. My usual cd-up looks like: $ cd ../../.. # Oops, not enough $ cd .. #...
3
votes
3answers
753 views

Are there any utilities to quickly add, list and remove command aliases?

I'd like to be able to quickly, on-the-fly add (and list/remove) command aliases so that they persist between shell restarts (as if they were added to .bashrc). Are there any ready utilities/scripts/...
342
votes
4answers
201k views

What is the difference between curl and wget?

I am keen to know the difference between curl and wget. Both are used to get files and documents but what the key difference between them. Why are there two different programs?
64
votes
3answers
136k views

How can I test the encoding of a text file… Is it valid, and what is it?

I have several .htm files which open in Gedit without any warning/error, but when I open these same files in Jedit, it warns me of invalid UTF-8 encoding... The HTML meta tag states "charset=ISO-8859-...
39
votes
5answers
11k views

Why use superflous dash (-) to pass option flags to tar?

To create a tar file for a directory, the tar command with compress, verbose and file options can be typed thus: $ tar -cvf my.tar my_directory/ But it also works to do it this way: $ tar cvf my....
15
votes
1answer
3k views

Understanding the output of the `who -a` command

I am asking this question because, while there are many answers on the internet showing that who -a is an option, nobody explains how to read the output. If you could provide a link to an online site ...
48
votes
8answers
5k views

Why are POSIX mandatory utilities not built into the shell?

The purpose of this question is to answer a curiosity, not to solve a particular computing problem. The question is: Why are POSIX mandatory utilities not commonly built into shell implementations? ...
29
votes
4answers
29k views

I try to add passwords to the “pass” password manager. But my attempts fail with “no public key” GPG errors. Why?

I am trying to install Pass: the standard Unix password manager, however, when I try to add passwords to the appliation I get these errors gpg: Kelly's Passwords: skipped: No public key gpg: [stdin]: ...
24
votes
7answers
92k views

Why is 'df' hanging?

I have recently been having problems running df, where it just hangs. Here's strace output, and in it, you'll see that I killed since it was just sitting there: $ strace /bin/df execve("/bin/df", ["/...
3
votes
1answer
5k views

Listing a hardrive partition by blocks using LBA

Most hard drive and partition inspection tools seem to list the items using sectors, head.. etc. From another question I was told that these are virtual because they have to be converted from lba, ...
9
votes
3answers
3k views

Combine input from multiple files/pipes without clobbering lines or blocking?

Is there a tool that will take input from multiple files or pipes and write it to stdout, without blocking on reads, such that individual input lines come out intact? I basically want to multiplex a ...
9
votes
3answers
650 views

Doing two things with output from a command

I have a program texcount that outputs the number of words in my LaTeX document. I can also pipe the output of this to sed to make the newlines TeX linebreaks and write this to a file which I can then ...
4
votes
2answers
2k views

Convert file with integers written in ascii to binary file of integers

I have a file that contains a long list of integers written in ascii separated with newlines, like such: -175 2 -19345 345592 -45 2355 etc... I want to convert this file into a "binary" file ...
15
votes
3answers
1k views

head eats extra characters

The following shell command was expected to print only odd lines of the input stream: echo -e "aaa\nbbb\nccc\nddd\n" | (while true; do head -n 1; head -n 1 >/dev/null; done) But instead it just ...
5
votes
2answers
2k views

Why is bash completion of a symlink different than a directory?

I usually do a find with an environment variable as the path when searching for source code. Recently I replaced my environment variable with a symbolic link, and it broke Bash's shell completion. ...
5
votes
9answers
3k views

Is there a shell command or utility for caching process output?

Hope this is the right place to ask. Is there a unix tool that works similarly to this? # invokes echo, saves to cache (using command with arguments as key), returns "hi" cache 10 echo hi # wait 2 ...
4
votes
4answers
1k views

Decomposition of path specs into longest-common-prefix + suffix

Given any two absolute Unix path specs1, one could decompose each spec as the concatenation of a longest common prefix and a specific suffix. E.g., /abc/bcd/cdf -> /abc/bcd + cdf /abc/bcd/chi/...
4
votes
3answers
3k views

Why doesn't uname -a return a useful identifier

I typed the command uname -a into my college's server and got this: 2.6.18-274.3.1.el5 #1 SMP Tue Sep 6 20:14:03 EDT 2011 i686 i686 i386 GNU/Linux Are they trying to hide the version of Linux that ...
2
votes
2answers
1k views

Is there any “base” Debian metapackage?

I've used Debian's Raspberry Pi image builder to create arm64 image, but the problem is it's too barebones. Are there any metapackages that installs useful tools, equivalent to Ubuntu's ubuntu-...
2
votes
2answers
144 views

Is there a distribution-independent tool to autocompile+install dependencies?

I like the way e.g. ArchLinux' yaourt (or if you're not that lazy, abs+makepkg; and from what I read so far, Gentoo's ebuild as well) automatically take care of obtaining, compiling and installing ...