71 Answered Questions for the topic UNIX

06/17/19

What is the Windows equivalent of the Unix command cat? ?

I want to do exactly what unix "cat" does, but on my PC. Is there a simple equivalent command for the Windows command line? Specifically I want to create a file from all the files of a given type... more

06/03/19

What is the fastest way to get the value of π?

I'm looking for the fastest way to obtain the value of π, as a personal challenge. More specifically, I'm using ways that don't involve using `#define` constants like `M_PI`, or hard-coding the... more

06/03/19

Delete newline in Vim?

Is there a way to delete the newline at the end of a line in Vim, so that the next line is appended to the current line? For example: Evaluator<T>(): _bestPos(){ } I'd like to put this... more

06/02/19

Extract file basename without path and extension in bash?

Given file names like these: /the/path/foo.txt bar.txt I hope to get: foo bar Why this doesn't work? #!/bin/bash fullfile=$1 fname=$(basename $fullfile) fbname=${fname%.*} echo... more

06/01/19

Argument list too long error for rm, cp, mv commands?

I have several hundred PDFs under a directory in UNIX. The names of the PDFs are really long (approx. 60 chars). When I try to delete all PDFs together using the following command: rm -f... more

05/30/19

Given two directory trees, how can I find out which files differ?

If I want find the differences between two directory trees, I usually just execute: diff -r dir1/ dir2/ This outputs exactly what the differences are between corresponding files. I'm interested... more

05/29/19

Aborting a shell script if any command returns a non-zero value?

I have a Bash shell script that invokes a number of commands. I would like to have the shell script automatically exit with a return value of 1 if any of the commands return a non-zero value. Is... more

05/29/19

Unix: How to check permissions of a specific directory?

I know that using `ls -l "directory/directory/filename"` tells me the permissions of a file. How do I do the same on a directory? I could obviously use `ls -l` on the directory higher in the... more

05/27/19

How to represent multiple conditions in a shell if statement?

I want to represent multiple conditions like this: if [ ( $g -eq 1 -a "$c" = "123" ) -o ( $g -eq 2 -a "$c" = "456" ) ] then echo abc; else echo efg; fi but when I execute the script,... more

05/26/19

Why should text files end with a newline?

I assume everyone here is familiar with the adage that all text files should end with a newline. I've known of this "rule" for years but I've always wondered — why?

05/26/19

How can I extract a predetermined range of lines from a text file on Unix?

I have a ~23000 line SQL dump containing several databases worth of data. I need to extract a certain section of this file (i.e. the data for a single database) and place it in a new file. I know... more

05/26/19

In Unix, can I run 'make' in a directory without cd'ing to that directory first?

In Unix, can I run 'make' in a directory without cd'ing to that directory first?

05/26/19

Remove carriage return in Unix?

What is the simplest way to remove all the carriage returns `\\r` from a file in Unix?

05/26/19

Concatenate multiple files but include filename as section headers?

I would like to concatenate a number of text files into one large file in terminal. I know I can do this using the cat command. However, I would like the filename of each file to precede the "data... more

05/26/19

Loop through an array of strings in Bash?

I want to write a script that loops through 15 strings (array possibly?) Is that possible? Something like: for databaseName in listOfNames then # Do something end

05/26/19

grep a tab in UNIX?

How do I `grep` tab (\ ) in files on the Unix platform?

05/26/19

How to assign name for a screen?

I'm using the `screen` multiplexer tool on the command shell and open a lot of screens. I then forget which process ID associates with which task. I would like to set a name for a screen but can't... more

05/26/19

How can I copy the output of a command directly into my clipboard?

How can I pipe the output of a command into my clipboard and paste it back when using a terminal? For instance: cat file | clipboard

05/26/19

grep, but only certain file extensions?

I am working on writing some scripts to `grep` certain directories, but these directories contain all sorts of file types. I want to `grep` just `.h` and `.cpp` for now, but maybe a few others in... more

05/25/19

How can I exclude directories from grep -R?

I want to traverse all subdirectories, except the "node_modules" directory.

05/24/19

Using ls to list directories and their total sizes?

Is it possible to use `ls` in Unix to list the total size of a sub-directory and all its contents as opposed to the usual 4K that (I assume) is just the directory file itself? I.E. total 12K ... more

05/23/19

How do I grep recursively?

How do I recursively `grep` all directories and subdirectories? find . | xargs grep "texthere" *

05/21/19

How to convert DOS/Windows newline (CRLF) to Unix newline (LF) in a Bash script?

How can I programmatically (i.e., not using `vi`) convert DOS/Windows newlines to Unix? The `dos2unix` and `unix2dos` commands are not available on certain systems. How can I emulate these with... more

05/21/19

How to run a shell script on a Unix console or Mac terminal?

I know it, forget it and relearn it again. Time to write it down.

05/21/19

How to split a large text file into smaller files with equal number of lines?

I've got a large (by number of lines) plain text file that I'd like to split into smaller files, also by number of lines. So if my file has around 2M lines, I'd like to split it up into 10 files... more
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