Commands by hemanth (21)

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Verify if user account exists in Linux / Unix

Remove text from file1 which is in file2 and stores it in an other file
This command compares file2 with file1 and removes the lines that are in file1 from file2. Handy if you have a file where file1 was the origional and you want to remove the origional data from your file2.

Rename files in batch

Get me yesterday's date, even if today is 1-Mar-2008 and yesterday was 29-Feb-2008
Fool date by setting the timezone out by 24 hours and you get yesterday's date. Try TZ=XYZ-24 to get tomorrow's date. I live in TZ=GMT0BST so you might need to shift the number 24 by the hours in your timezone.

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"

ssh autocomplete
Autocomplete from .ssh/config

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" }

Vectorize xkcd strips
Uses ImageMagick and potrace to vectorize the input image, with parameters optimized for xkcd-like pictures.

Summary of disk usage, excluding other filesystems, summarised and sorted by size
This command is useful for finding out which directories below the current location use the most space. It is summarised by directory and excludes mounted filesystems. Finally it is sorted by size.

Detect illegal access to kernel space, potentially useful for Meltdown detection
Based on capsule8 agent examples, not rigorously tested


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