Commands by tebeka (7)

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Execute a command with a timeout
In this example the command "somecommand" will be executed and sent a SIGALARM signal if it runs for more than 10 seconds. It uses the perl alarm function. It's not 100% accurate on timing, but close enough. I found this really useful when executing scripts and commands that I knew might hang E.g. ones that connect to services that might not be running. Importantly this can be used within a sequential script. The command will not release control until either the command completes or the timeout is hit.

Take a screenshot every 2 seconds
Take a screenshot every 2 seconds and save it as a png file

Find usb device
I often use it to find recently added ou removed device, or using find in /dev, or anything similar. Just run the command, plug the device, and wait to see him and only him

Debug redirects between production reloads
Watches the headers of a curl, following any redirects and printing only the HTTP status and the location of the possible redirects.

Lists all directories under the current dir excluding the .svn directory and its contents

Rename files in batch

Execute a command with a timeout
A timeout is great, but what if the command is taking longer than expected because it's hung up or ran into some other problem? That's where the -k option comes in. Run "some_command" and timeout after 30s. If the command is still running after 1 minute, it will receive a kill signal.

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" }

New command with the last argument of the previous command.

Tail a log file with long lines truncated
This truncates any lines longer than 80 characters. Also useful for looking at different parts of the line, e.g. cut -b 50-100 shows columns 50 through 100.


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