Below is a list of useful bash commands for everyday work. I have just created the repository, more contents shall be added soon.
Audio and Video
Get bash script here.
Trim audio
ffmpeg -ss 20 -i input.mp3 -t 10 -c copy output.mp3
The option -ss 20 starts trimming from 20 sec of the input audio and -t 10 signifies that output audio length is 10 sec.
Concatenate audio
mp3wrap output.mp3 input1.mp3 input2.mp3
Merge video and audio
With audio re-encoding
ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac output.mp4
Without audio re-encoding
ffmpeg -i video.mp4 -i audio.wav -c copy output.mkv
Replacing audio stream
ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4
Merge video and subtitle (.srt) file
ffmpeg -i video.mp4 -i subtitle.srt -c copy -c:s mov_text output.mp4
Dates and Times
Get bash script here.
View Clock with xclock
xclock -update 1 -geom 900x900
The -update option signifies how often the clock is updated in seconds. The -geom or -geometry is the resolution (size) of the clock.
View calender with cal
cal
To print the current year’s calendar, use
cal -y
Putting a year after -y prints calender of that year.
View dates and times with date
date
Download
Download with wget
Simply put the URL of the file you want to download as an argument to wget.
wget [URL]
To download file and save under specific name, run
wget -0 [name] [URL]
To download in background, run
wget -b [URL]
Resume download with wget
To resume/continue downloading a file, run
wget -c [URL]
Download multiple files with wget
Make a list of all the URLs (one per line) in a text file downloadlist.txt and then run
wget -i downloadlist.txt
Images
Resize images
To reduce the size of the image input.jpg to 40%, run
convert -resize 40% input.jpg output.jpg
The target size may also be specified:
convert -resize 720x480 input.jpg output.jpg
Convert transparent PNG to JPG by adding background
The following example converts image.png to image.jpg by adding a white background
convert image.png -background white -flatten -alpha off image.jpg
Metadata
We are using ImageMagick here. To read metadata, use
identify -verbose /path/image.jpg | grep exif
To remove all metadata, use
mogrify -strip /path/image.jpg
PDFs
Get bash script here.
Turn images into PDFs
convert 1.jpg 2.jpg output.pdf
To convert all JPG images in the directory, use
convert *.jpg output.pdf
Extract pages from PDFs
To extract pages 10-12, 15 and 21-22 from input.pdf and compile them into out.pdf, use
pdftk input.pdf cat 10-12 15 21-22 output out.pdf
Extract imbedded images from PDFs
To extract images in their original formats:
pdfimages -all input.pdf /tmp/out
To extract images in JPEG:
pdfimages -j input.pdf /tmp/out
Merge several pdf files into one pdf file
pdftk infile1.pdf infile2.pdf infile3.pdf cat output outfile.pdf