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1500 questions
92
votes
2 answers

Trim audio file using start and stop times

I have an FFmpeg command to trim audio: ffmpeg -ss 01:43:46 -t 00:00:44.30 -i input.mp3 output.mp3 The problem I have with this command is that option -t requires a duration (in seconds) from 01:43:46. I want to trim audio using start/stop times,…
whitewings
  • 2,457
92
votes
2 answers

What is the difference between .a and .so file?

As far as I understand they are libraries, but what is the difference between the two?
Erik B
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92
votes
9 answers

Can sed replace new line characters?

Is there an issue with sed and new line character? I have a file test.txt with the following contents aaaaa bbbbb ccccc ddddd The following does not work: sed -r -i 's/\n/,/g' test.txt I know that I can use tr for this but my question is…
Jim
  • 10,120
91
votes
7 answers

How safe is it to cat an arbitrary file?

Sometimes when I cat a binary file by mistake, my terminal gets garbled up. Nothing a quick reset can't fix, but couldn't an attacker theoretically create a file that, when displayed on a terminal, would execute some arbitrary code? Through an…
Gunchars
  • 1,001
91
votes
6 answers

Why do iptables rules disappear when restarting my Debian system?

I add this rule: sudo iptables -t nat -A OUTPUT -d a.b.c.d -p tcp \ --dport 1723 -j DNAT --to-destination a.b.c.d:10000 When restart computer rules are deleted. Why? What I can do to make the rules persist?
Jhonathan
  • 3,605
91
votes
8 answers

Ubuntu update error: "waiting for unattended-upgr to exit"

I'm unable to update my system having two installations of Ubuntu: One is version 16.04 and the other version is 17.04. In both, I'm getting the same error. For ex., in Ubuntu 16.04, I run software updater and get the result as shown below. I did…
Ravi
  • 3,823
91
votes
6 answers

How to exit a shell script if one part of it fails?

How can I write a shell script that exits, if one part of it fails? For example, if the following code snippet fails, then the script should exit. n=0 until [ $n -ge 5 ] do gksu *command* && break n=$[$n+1] sleep 3
Weylyn
  • 935
91
votes
4 answers

How to OCR a PDF file and get the text stored within the PDF?

First, apologies if this has been asked before - I searched for a while through the existing posts, but could not find support. I am interested in a solution for Fedora to OCR a multipage non-searchable PDF and to turn this PDF into a new PDF file…
ingli
  • 1,847
91
votes
4 answers

How to recover a 'lost' screen session?

Somehow I managed to close a screen window without screen 'noticing' it, so the session is still flagged as attached. This prevents me from re-attaching to this session. What can I do? me@iupr-serv8:~$ screen -r There are several suitable screens…
Framester
  • 1,633
91
votes
9 answers

How do I split an audio file into multiple?

I found something for videos, which looks like this. ffmpeg -i * -c:v libx264 -crf 22 -map 0 -segment_time 1 -g 1 -sc_threshold 0 -force_key_frames "expr:gte(t,n_forced*9)" -f segment output%03d.mp4 I tried using that for an audio file, but only…
DisplayName
  • 11,688
91
votes
5 answers

Refresh env variables after editing bashrc file

I frequently edited the .bashrc file to export new environment variables. Rather than close the console and start a new one to refresh the env variables, is there a convenient way to refresh?
xiaohan2012
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91
votes
2 answers

How to tell journald to re-read its configuration?

My question is simple: how do I tell journald to re-read its configuration file without rebooting? I've made some changes to /etc/systemd/journald.conf and I'd like to see if they are correct and everything works as I expect. I do not want to…
lorenzog
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91
votes
5 answers

Merge two video clips into one, placing them next to each other

I have two video clips. Both are 640x480 and last 10 minutes. One contains background audio, the other one a singing actor. I would like to create a single 10 minute video clip measuring 1280x480 (in other words, I want to place the videos next to…
user
  • 1,005
91
votes
3 answers

Piping commands after a piped xargs

HP-UX ***** B.11.23 U ia64 **** unlimited-user license find . -type d -name *log* | xargs ls -la gives me the directory names (the ones which contain log in the directory name) followed by all files within that directory. The directories …
anotherperson1
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91
votes
2 answers

Understand logging in Linux

As I understand, Linux kernel logs to /proc/kmsg file(mostly hardware-related messages) and /dev/log socket? Anywhere else? Are other applications also able to send messages to /proc/kmsg or /dev/log? Last but not least, am I correct that it is the…
Martin
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