20
votes
4answers
6k views

Evolution of Operating systems from Unix

Can you explain the evolution hierarchy of operating systems (Linux and Windows) from Unix?
37
votes
5answers
9k views

What process created this X11 window?

Given an X11 window ID, is there a way to find the ID of the process that created it? Of course this isn't always possible, for example if the window came over a TCP connection. For that case I'd ...
27
votes
4answers
2k views

Quick way to include a directory path when calling mv? [duplicate]

Often I will work out of the root of a rails directory where I find my self navigating the same path twice every time I would like to move a file: mv app/views/layouts/application.html.erb ...
14
votes
1answer
19k views

File descriptors & shell scripting

I am having a very hard time understanding how does one use file descriptors in shell scripts. I know the basics such as exec 5 > /tmp/foo So fd 5 is attached to foo for writing. exec 6 < ...
24
votes
2answers
4k views

Can I get individual man pages for the bash builtin commands? [duplicate]

Is there anywhere you can download a manpage for every builtin commands? I know you can just use help or man bash and search to find info about it, but I want them separated, so I can just do man ...
24
votes
3answers
1k views

What is the difference between [[ $a == z* ]] and [ $a == z* ]?

Is there is any difference between these two. [[ $a == z* ]] and [ $a == z* ] Can I have an example where they would have different outputs? Furthermore, how does the working of [[ ]] differs ...
20
votes
7answers
1k views

Reading and searching long man pages

I finally got fed up when wanting to read about bash's read and it's -s option with man bash. I found the right spot eventually (around line 4500), but it was a frustrating as usual, since both /read ...
21
votes
2answers
18k views

How to colorize output of ls ?

I'm running CentOS in Linux text mode. When I run the command ls /usr/, the output is too hard to read (dark blue on black). How can I change the text coloring?
11
votes
3answers
2k views

Trapping errors in command substitution using “-o errtrace” (ie set -E)

According to this ref manual: -E (also -o errtrace) If set, any trap on ERR is inherited by shell functions, command substitutions, and commands executed in a subshell environment. The ERR ...
17
votes
4answers
31k views

How to escape quotes in shell?

I'm having trouble with escaping characters in bash. I'd like to escape single and double quotes while running a command under a different user. For the purposes of this question let's say I want to ...
33
votes
1answer
3k views

Does 'rm .*' ever delete the parent directory?

The expression .* is expanded by bash to include the current and parent directories: $ ls -la total 2600 drwxrwxrwx 2 terdon terdon 2162688 Sep 10 16:22 . drwxr-xr-x 142 terdon terdon 491520 Sep ...
12
votes
3answers
28k views

Extracting a regex matched with 'sed' without printing the surrounding characters

To all the 'sed' doctors out there: How can you get 'sed' to extract a regular expression it has matched in a line? In other words words, I want just the string corresponding to the regular ...
10
votes
2answers
4k views

How to restrict internet access for a particular user on the lan using iptables in Linux

Let's say there are two users on the LAN, A and B. How do I restrict user A from internet access using iptables rules and saving the rules so that after reboot, they are still effective. And suppose I ...
18
votes
3answers
7k views

What defines the maximum size for a command single argument?

I was under the impression that the maximum length of a single argument was not the problem here so much as the total size of the overall argument array plus the size of the environment, which is ...
7
votes
7answers
18k views

Transposing rows and columns

I have a file with the lines like below. title1:A1 title2:A2 title3:A3 title4:A4 title5:A5 title1:B1 title2:B2 title3:B3 title4:B4 title5:B5 title1:C1 title2:C2 title3:C3 title4:C4 title5:C5 ...
12
votes
2answers
5k views

Mapping key combination with xmodmap

I'm trying to achieve the following mapping keycode 135 = <Ctrl-C> Is it possible to achieve this in some way?
7
votes
2answers
2k views

Portability of file descriptor links

I've always wondered this but never took the time to find out, so I'll do so now - how portable is the usage shown here of either /proc/$$/fd/$N or /dev/fd/$N? I understand POSIX guarantees /dev/null, ...
8
votes
3answers
2k views

Linux Bulk/Remote Administration

Beside our internal IT infrastructure, we've got around 500 Linux machines hosting our services for the on-line world. They are grouped in a bunch of clusters like Database A-n, Product A-n, NFS, ...
10
votes
2answers
1k views

Bash -c with positional parameters

Usually, $0 in a script is set to the name of the script, or to whatever it was invoked as (including the path). However, if I use bash with the -c option, $0 is set to the first of the arguments ...
10
votes
5answers
1k views

What's the best way to take a segment out of a text file?

What's a good way of extracting say, lines 20 -45 out of a huge text file. Non-interactively of course!
10
votes
6answers
9k views

How do I recursively grep through compressed archives?

I'm trying to find out what modules use Test::Version in cpan. So I've used minicpan to mirror it. My problem is that I need to iterate through the archives that are downloaded, and grep the files ...
4
votes
1answer
5k views

Rename All Files with a Certain Name

I'm trying to find certain files with the name "stringx" and replace the name (but not the extension) with "stringy". So basically for stringx.txt and stingx.cs, I'd want stringy.txt and stringy.cs. ...
2
votes
3answers
454 views

command not found and syntax error near unexpected token

I have this script to divide a file over a 100000 or even more in 50000 lines. desc() { echo ...
241
votes
3answers
139k views

How to unfreeze after accidentally pressing Ctrl-S in a terminal?

It's a situation that has happened quite often to me: after I press (with a different intention) Ctrl-S in a terminal, the interaction (input or output) with it is frozen. It's probably a kind of ...
219
votes
32answers
169k views

Tracking down where disk space has gone on Linux?

When administering Linux systems I often find myself struggling to track down the culprit after a partition goes full. I normally use du / | sort -nr but on a large filesystem this takes a long time ...
66
votes
6answers
57k views

What is a Superblock, Inode, Dentry and a File?

From the article Anatomy of the Linux file system by M. Tim Jones, I read that Linux views all the file systems from the perspective of a common set of objects and these objects are superblock, inode, ...
120
votes
4answers
155k views

How to run find -exec?

I'd like to find the files in the current directory that contain the text "chrome". $ find . -exec grep chrome find: missing argument to `-exec' What am I doing wrong?
76
votes
5answers
53k views

How can I send stdout to multiple commands?

There are some commands which filter or act on input, and then pass it along as output, I think usually to stdout - but some commands will just take the stdin and do whatever they do with it, and ...
56
votes
6answers
2k views

Resources for portable shell programming

What resources exist for portable shell programming? The ultimate answer is to test on all targeted platforms, but that's rarely practical. The POSIX / Single UNIX specification is a start, but it ...
70
votes
9answers
32k views

How to check if a shell is login/interactive/batch

I think I understand the differences between an interactive, a login and a batch shell. See the following links for more help: What is the difference between a 'Login' and an 'Interactive' bash ...
97
votes
6answers
40k views

Can I create a user-specific hosts file to complement /etc/hosts?

Is it possible to add a list of hosts that are only specific to a certain user? Perhaps a user-specific hosts file? This mechanism should also complement the entries in the /etc/hosts file.
70
votes
14answers
37k views

How to grep a specific line _and_ the first line of a file?

Assuming a simple grep such as: $ psa aux | grep someApp 1000 11634 51.2 0.1 32824 9112 pts/1 SN+ 13:24 7:49 someApp This provides much information, but as the first line of the ps ...
69
votes
9answers
4k views

Remember a half-typed command while I check something

I often find myself in the following position: I've started typing a long command at the bash prompt, but half-way through I find out I need to check something with another command. This is a problem ...
40
votes
2answers
18k views

su vs sudo -s vs sudo -i vs sudo bash

What is the difference between the following commands: su sudo -s sudo -i sudo bash I know for su I need to know the root password, and for sudo I have to be in the sudoers file, but once executed ...
69
votes
4answers
67k views

How big is the pipe buffer?

As a comment in I'm confused as to why "| true" in a makefile has the same effect as "|| true" user cjm wrote: Another reason to avoid | true is that if the command ...
43
votes
11answers
45k views

How can I reliably get the operating system's name?

Say I am logged into a remote system, how can I know what it's running? On most modern Linuxes (Linuces?), you have the lsb_release command: $ lsb_release -ic Distributor ID: LinuxMint Codename: ...
25
votes
1answer
55k views

How to loop over the lines of a file?

Say I have this file: hello world hello world This program #!/bin/bash for i in $(cat $1); do echo "tester: $i" done outputs tester: hello tester: world tester: hello tester: world I'd ...
36
votes
8answers
63k views

Correctly determining memory usage in Linux

I'm a bit confused on some of the results I am seeing from ps and free. On my server, this is the result of free -m [root@server ~]# free -m total used free shared ...
37
votes
15answers
13k views

Detect init system using the shell

This may have more to do with detecting operating systems, but I specifically need the init system currently in use on the system. Fedora 15 now uses systemd, Ubuntu uses Upstart, while others use ...
19
votes
2answers
8k views

Where should a local executable be placed?

I have an executable for the perforce version control client (p4). I can't place it in /opt/local because I don't have root privileges. Is there a standard location where it needs to be placed under ...
38
votes
5answers
15k views

Measuring RAM usage of a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can measure the max RAM usage of the program and any children. ...
21
votes
3answers
13k views

Understanding /dev and its subdirs and files

$ ls -l /dev/stdin /dev/fd/0 lrwx------ 1 tim tim 64 2011-08-07 09:53 /dev/fd/0 -> /dev/pts/2 lrwxrwxrwx 1 root root 15 2011-08-06 08:14 /dev/stdin -> /proc/self/fd/0 $ ls -l /dev/pts/2 ...
19
votes
4answers
9k views

Four tasks in parallel… how do I do that?

I have a bunch of PNG images on a directory. I have an application called pngout that I run to compress these images. This application is called by a script I did. The problem is that this script does ...
49
votes
3answers
65k views

How do I do a ls and then sort the results by date created?

In what order are the dated ordered by? Certainly not alphanumeric order. ls -lt sorts by modification time. But I need creation time.
22
votes
3answers
14k views

Determining Specific File Responsible for High I/O

This is a simple problem but the first time I've ever had to actually fix it: finding which specific files/inodes are the targets of the most I/O. I'd like to be able to get a general system overview, ...
27
votes
3answers
16k views

List the files accessed by a program

time is a brilliant command if you want to figure out how much CPU time a given command takes. I am looking for something similar that can list the files being accessed by a program and its children. ...
23
votes
4answers
143k views

Limit FTP access only to the /var/www with vsftpd

I am running vsftpd as ftp server on my linux (rasbian), I log in to the machine as a root user. I would like to be still locked to using only /var/www, how can I configure vsftpd conf to accomplish ...
21
votes
4answers
7k views

Why does dd from /dev/random give different file sizes?

I am running the following command on an ubuntu system: dd if=/dev/random of=rand bs=1K count=2 However, every time I run it, I end up with a file of a different size. Why is this? How can I ...
36
votes
2answers
16k views

What do the brackets around processes mean?

mark@mark-VirtualBox:~/auto/lib$ ps -Awwo pid,comm,args PID COMMAND COMMAND 1 init /sbin/init 2 kthreadd [kthreadd] 3 ksoftirqd/0 [ksoftirqd/0] 5 ...
26
votes
7answers
6k views

how to glob every hidden file except current and parent directory [duplicate]

I want to glob every hidden file and directory, but not the current (.) and parent directory (..). I am using bash. Observe current behaviour: $ ls -a . .. ...a ...aa ..a ..aa .a .aa .aaa ...

15 30 50 per page