In Golang, how to convert a string to unicode rune array and do the reverse way? Convert string s to a rune array: runes := []rune(s) Convert a rune array runes to string: str := string(runes)
In Golang, fmt.Println(err) can print out the error err. But how to convert an error to a string explicitely? In Go, the error type is an interface type that has an interface type error interface { Error() string } An error variable represents any value that can describe itself as a string. Ref: https://golang.org/pkg/builtin/#error So,…
The dmesg results from newer Linux kernels show the timestamps. It seems the time in seconds since the kernel start time. How to convert the dmesg timestamps to the real time on Linux? The dmesg timestamp is the time in seconds since the kernel starting time. Later dmesg has an -T option: -T, –ctime Print…
The samtools merge can merge bam files while it can not work for sam files. How to merge sam files on Linux? According to the sam format specification, header lines start with @, while alignment lines do not. So you can use grep to merge sam files as follows efficiently. Assume the header is from…
I have a poster to be submitted to the publisher which requires image files in CMYK color. The file I already have is in RGB color. How to convert it on Linux? The convert tool from ImageMagick with option -colorspace to alternate image colorspace of images. The plain output with colorspace is quite large. So…
How to convert PDF to text with format kept on Linux? Many of the formatting in PDF will not be available in text. But better keep the text’s relative positions as the same. For example, the table columns should be kept. The pdftotext tool can convert PDF to text pretty well: pdftotext – Portable Document…
How to convert general JavaScript objects to json in Node.js? Assume jo is a JavaScript object, you can convert it to a json string by: JSON.stringify(jo)
How to convert all text in a file from upper case to lower case and vice versa on Linux? Convert from upper case to lower case: tr ‘[:upper:]’ ‘[:lower:]’ < input.txt > output.txt Convert from lower case to upper case: tr ‘[:lower:]’ ‘[:upper:]’ < input.txt > output.txt
convert seems works not very well when merging PDFs. The quality is low. Any other better methods to merge multiple PDF files to a single PDF on Linux? ghostscript works the best for me on merging PDFs: gs -q -sPAPERSIZE=letter -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=out.pdf in1.pdf in2.pdf in3.pdf merges in{1..3}.pdf to out.pdf.
How to convert .pptx slides to .jpg or .png images on Linux in command line? This following method works best for me. First, convert .pptx file to .pdf using libreoffice: libreoffice –headless –convert-to pdf file.pptx –headless makes libreoffice run in batch mode and not start the GUI. The pdf file will be named file.pdf by…
How to convert between Simplified Chinese and Traditional Chinese characters in text files on Linux from command line? You can use opencc to convert between Traditional Chinese and Simplified Chinese: https://github.com/BYVoid/OpenCC For example, to transfer a file in simplified Chinese sc.txt to traditional Chinese: opencc -i sc.txt -o tc.txt -c zhs2zht.ini The authors also provide…
How to play 3D movies in MPlayer on normal screen (2D)? You can play 3D movies on 2D screen by mplayer -vo gl_stereo=3 your.movie.file For the gl:stereo=3 option, check MPlayer man page: stereo=value Select a method for stereo display. You may have to use -aspect to fix the aspect value. Add 32 to swap left…
Resizing images on Linux with gThumb is easy. However, I have a batch of images inside a folder. Manually resizing them will consume too much time. How to automatically resize them on Linux with a script? You can use convert from ImageMagick together with bash script to resize images inside a directory. mkdir resize; IFS=$(echo…
How to detect whether a .jpg image is almost blank/black on Linux? Here is a bash function that I used to detect whether an image is black on Linux: function isBlank () { mean=`convert $1 -format “%[mean]” info:` echo “$mean” } It uses ImageMagic to generate formatted image characteristics (the mean). If the mean is…
I have multiple jpg images as files like 001.jpg, 002.jpg … How to merge multiple jpg images to a pdf on Linux? convert is your good friend: convert *.jpg output.pdf
When use gitbook to generate ebook, Calibre reports this: RuntimeError: X server required. If you are running on a headless machine, use xvfb After xvfb is installed, it does not work either. How to make gitbook/Calibre work on a headless server? You need to wrap the command ebook-convert with xvfb-run. However, in gitbook (lib/generate/ebook/index.js), ebook-convert…
How to convert a video file in format as flv to mp4 with ffmpeg? You may use method from here: https://www.systutorials.com/3540/converting-video-files-for-ipod-iphone-ipad/ ffmpeg -i input.flv output.mp4 Or by specifying more details about how to handling the codecs: ffmpeg -i input.flv -vcodec copy -acodec copy output.mp4 You may also add more options as you like. For more,…
The disk management tools of Windows can adjust it to some level. But there are more space available as far as I can tell. How to further adjust the system partition (C:) size of Windows? You may check these tools: EASEUS Partition Master (free) Includes Partition Manager, Disk & Partition Copy Wizard and Partition Recovery…
How to convert between dos and unix file coding for files in Emacs? From Dos to Unix coding: M-x set-buffer-file-coding-system RET undecided-unix or C-x RET f undecided-unix Then save the file (C-x C-s). From Unix to Dos M-x set-buffer-file-coding-system RET undecided-dos or C-x RET f undecided-dos Then save the file (C-x C-s).
How to replace tabs with spaces in Emacs? You can first select the regions of text for converting/replacing, then run M-x untabify to replace all tabs with appropriate number of spaces. There is also a M-x tabify for replacing sequences of spaces to tabs. There are also commands to convert tabs to spaces or vice…