Commands by chuckr (3)

What's this? is the place to record those command-line gems that you return to again and again. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.

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recursively change file name from uppercase to lowercase (or viceversa)
easier way to recursively change files to lowercase using rename instead

Exclude a string with awk

Download all files from podcast RSS feed
Neither of the others worked for me. This does.

Create arbitrary big file full of zeroes but done in a second
If you want to create fast a very big file for testing purposes and you do not care about its content, then you can use this command to create a file of arbitrary size within less than a second. Content of file will be all zero bytes. The trick is that the content is just not written to the disk, instead the space for it is somehow reserved on operating system level and file system level. It would be filled when first accessed/written (not sure about the mechanism that lies below, but it makes the file creation super fast). Instead of '1G' as in the example, you could use other modifiers like 200K for kilobytes (1024 bytes), 500M for megabytes (1024 * 1024 bytes), 20G for Gigabytes (1024*1024*1024 bytes), 30T for Terabytes (1024^4 bytes). Also P for Penta, etc... Command tested under Linux.

Bash prompt with user name, host, history number, current dir and just a touch of color
I put that line in my .bash_profile (OS X) and .bashrc (Linux). Here is a summary of what the \char means: n=new line, u=user name, h=host, !=history number, w=current work directory The \[\e[32m\] sequence set the text to bright green and \[\e[0m\] returns to normal color. For more information on what you can set in your bash prompt, google 'bash prompt'

Convert all .flac from a folder subtree in 192Kb mp3
find . -type f -iname '*.flac' # searches from the current folder recursively for .flac audio files | # the output (a .flac audio files with relative path from ./ ) is piped to while read FILE; do FILENAME="${FILE%.*}"; flac -cd "$FILE" | lame -b 192 - "${FILENAME}.mp3"; done # for each line on the list: # FILE gets the file with .flac extension and relative path # FILENAME gets FILE without the .flac extension # run flac for that FILE with output piped to lame conversion to mp3 using 192Kb bitrate

To Stop or Start (Restart) a Windows service from a Linux machine

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Show apps that use internet connection at the moment.
This corrects duplicate output from the previous command.

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

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