Linux commands

Write to a file from with cat:

$ cat << EOF > filename
# enter text
> EOF

Setting and unsetting environment variables:

$ export VARIABLE_NAME=new-variable-name
$ unset VARIABLE_NAME

Create dirs and files quickly:

$ mkdir -p /tmp/testdir/{text,logs}
$ touch /tmp/testdir/text/{text1,text2,text3}.txt
$ touch /tmp/testdir/logs/{log1,log2,log3}.log

Copy multiple files from a directory:

$ cp ../tool/{add.go,go.mod} .

Creating cron job:

$ crontab -e # opens visual editor
$ 

Switch back to the previous working directory:

$ cd -

time executes an application and logs to the console how long it takes to run:

$ time ./colstats -op avg -col 3 testdata/example.csv testdata/example2.csv 
233.84

real	0m0.005s
user	0m0.006s
sys	0m0.000s

In the preceding example, real shows the total elapsed time.

The tee command logs command output to STDOUT and writes it to a file:

$ go test -bench . -benchtime=10x -run ^$ | tee benchresults00.txt
goos: linux
goarch: amd64
pkg: colstats
cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
BenchmarkRun-12    	      10	 546183149 ns/op
PASS
ok  	colstats	6.067s

$ cat benchresults00.txt 
goos: linux
goarch: amd64
pkg: colstats
cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
BenchmarkRun-12    	      10	 546183149 ns/op
PASS
ok  	colstats	6.067s

TODO Learn how cURL works

curl -L -XPOST -d '{"task":"Task 1"}' -H 'Content-Type: application/json' http://localhost:8080/todo

Compress files

Unzip .zip files with unzip. Do not include a directory if you want to unzip it to the current working directory:

$ unzip file.zip -p /unzip/to/this/dir

Extract contents of a tar file with tar:

$ tar -xzvf filename.tar.gz -C targetDir/

View compressed file info:

$ gzip -l *
         compressed        uncompressed  ratio uncompressed_name
               1229                3047  61.1% experiment_toolid_test.go
               1021                2106  53.3% overlaydir_test.go
                696                1320  49.8% reboot_test.go
               2946                6473  55.0% (totals)

cURL

Use the -i flag to display HTTP response headers with the body:

$ curl -i localhost:4000/v1/healthcheck

-d flag

The following command annotates the HTTP response with the total time for the command to complete:

$ curl -w '\nTime: %{time_total}s \n' localhost:4000/v1/movies/1

https://blog.josephscott.org/2011/10/14/timing-details-with-curl/

xargs TODO

https://man7.org/linux/man-pages/man1/xargs.1.html

$ xargs -I % -P8 curl -X PATCH -d '{"runtime": "97 mins"}' "localhost:4000/v1/movies/4" < <(printf '%s\n' {1..8})