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1500 questions
107
votes
3 answers
Why can rm remove read-only files?
If I create a file and then change its permissions to 444 (read-only), how come rm can remove it?
If I do this:
echo test > test.txt
chmod 444 test.txt
rm test.txt
...rm will ask if I want to remove the write-protected file test.txt. I would have…
Magnus
- 1,413
107
votes
4 answers
What does "3>&1 1>&2 2>&3" do in a script?
I saw this line in a script:
DEVICE=`dialog --inputbox "Festplatten-Laufzeit auslesen. Gebe Sie das
gewünschte Device an: " 0 70 "" 3>&1 1>&2 2>&3`
What is
3>&1 1>&2 2>&3
doing? I know that 1 = stdout and 2 = stderr, but what are the 3 and the &…
jsterr
- 1,341
107
votes
5 answers
Systemd Restart=always is not honored
Note: I wrote an article on Medium that explains how to create a service, and how to avoid this particular issue: Creating a Linux service with systemd.
Original question:
I'm using systemd to keep a worker script working at all…
BenMorel
- 4,587
107
votes
3 answers
Why does bashrc check whether the current shell is interactive?
On my Arch install, /etc/bash.bashrc and /etc/skel/.bashrc contain these lines:
# If not running interactively, don't do anything
[[ $- != *i* ]] && return
On Debian, /etc/bash.bashrc has:
# If not running interactively, don't do anything
[ -z…
terdon
- 242,166
107
votes
5 answers
Using awk to sum the values of a column, based on the values of another column
I am trying to sum certain numbers in a column using awk. I would like to sum just column 3 of the "smiths" to get a total of 212. I can sum the whole column using awk but not just the "smiths". I have:
awk 'BEGIN {FS = "|"} ; {sum+=$3} END {print…
jake
- 1,215
- 2
- 10
- 9
107
votes
5 answers
Restart bash from terminal without restarting the terminal application (mac)?
I've looked around and bit for an answer to this question but I don't seem to find it (which is weird).
My question is, is there any simple way to restart the BASH session from within the terminal on Mac. I just want the same behaviour as if I…
Mattias
- 1,587
107
votes
7 answers
How to use command line to change volume?
I am trying to control the volume using my programming script. How can I do the following in Fedora 15, Ubuntu linux?
Mute/ Unmute
Volume up and volume down
Note: Please note that I use a web USB microphone/speaker and also Analogue…
user11085
107
votes
2 answers
how to count the length of an array defined in bash?
I'm new to bash and can't find a good tutorial to answer my question.
array=( item1 item2 item3 )
for name in ${array[@]}; do
echo current/total
... some other codes
done
I want to calculate the current and total value, as the expected…
AGamePlayer
- 7,605
107
votes
3 answers
How can I create a virtual ethernet interface on a machine without a physical adapter?
I have a Dell XPS 13 ultrabook which has a wifi nic, but no physical ethernet nic (wlan0, but no eth0). I need to create a virtual adapter for using Vagrant with NFS, but am finding that the typical ifup eth0:1... fails with ignoring unknown…
STW
- 2,261
- 5
- 20
- 23
107
votes
4 answers
How to undo `set -x`?
I typed set -x in terminal.
Now the terminal keeps printing the last command run on top of my output so the command
~]$echo "this is what I see"
returns
+ echo 'this is what I see'
this is what I see
There is no man page for set, how do I turn…
lonewarrior556
- 2,083
107
votes
7 answers
command to determine ports of a device (like /dev/ttyUSB0)
I have a question regarding the ports in Linux. If I connect my device via USB and want to check its port I can't do it using the command lsusb, which only specifies bus number and device number on this bus:
[ziga@Ziga-PC ~]$ lsusb
Bus 003 Device…
71GA
- 1,106
107
votes
6 answers
Difference between ls -l and ll?
I'm relatively new to programming as a whole and some tutorials have been telling me to use ls -l to look at files in a directory and others have been saying ll. I know that ls is a short list, but is there a difference between the other two?
Jon
- 1,191
107
votes
8 answers
Into which directory should I install programs in Linux?
I want to install a program in Linux and run it as a daemon. (Team Speak 3 in this case, but the question is general in nature). There is no package provided, only tarred binaries.
Where in the directory structure should I put such a program by…
Eiver
- 1,225
107
votes
11 answers
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 when I'm at the console (no X), which is often…
Lauritz V. Thaulow
- 3,519
106
votes
5 answers
Bash throws error, line 8: $1: unbound variable
I am trying to learn how to use getopts so that I can have scripts with parsed input (although I think getopts could be better). I am trying to just write a simple script to return partition usage percentages. The problem is that one of my bash…
Timothy Pulliam
- 3,723