Commands tagged tty-dependant (1)

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Replace multiple file extensions with a single extension
The above is just a prove of concept based around the nested bash substitution. This could be useful in situations where you're in a directory with many filetypes but you only want to convert a few. $ for f in *.bmp *.jpg *.tga; do convert $f ${f%.*}.png; done or you can use ls | egrep to get more specific... but be warned, files with spaces will cause a ruckus with expansion but the bash for loop uses a space delimited list. $ for f in $(ls | egrep "bmp$|jpg$|tga$"); do convert $f ${f%.*}.png; done I'm guessing some people will still prefer doing it the sed way but I thought the concept of this one was pretty neat. It will help me remember bash substitutions a little better :-P

list with full path

Generate diff of first 500 lines of two files
Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

change ownership en masse of files owned by a specific user, including files and directories with spaces
In the example, uid 0 is root. foo:foo are the user:group you want to make owner and group. '.' is the "current directory and below." -print0 and -0 indicate that filenames and directories "are terminated by a null character instead of by whitespace."

quickly backup or copy a file with bash
less symbols, tab completion. including # export SIMPLE_BACKUP_SUFFIX="_`date +%F`" in your .bashrc provides you to easily timestamp your files

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Go to the next sibling directory in alphabetical order
Sometimes you have to browse your way through a lot of sub-directories. This command cd to the next sub-directory in alphabetical order. For example, if you have the directories "lectures/01-intro", "lectures/02-basic", "lectures/03-advanced" and so on, and your PWD is "02-basic", it jumps to "03-advanced".

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

Converting video file (.flv, .avi etc.) to .3gp
ffmpeg -i = input file name -s = set frame size, qcif=176x144 -vcodec = force video codec -r = frame-rate [default = 25] -b = bit-rate [200 kb/s] -acodec = force audio codec -ab = audio bitrate in bits/s [64k] -ac = no. of audio channels [1] -ar = audio sampling frequency [44100 Hz] optional: -sameq = use same video quality as source (implies VBR) -f = force format -y = overwrite output files

resolve short urls
since the most url shorteners respond with a header containing the Location: ... this works with most common shorteners


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