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114 lines
2.9 KiB
114 lines
2.9 KiB
2 years ago
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## Env-format
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### Instructions
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Create a script `env-format.sh`, which will print the environment variables that have the following formats:
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- Print the `PWD` value.
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- All the environment variables that have a letter `H` in the name, without printing the value of those variables.
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```console
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$ print env
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SHELL=/bin/bash
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QT_ACCESSIBILITY=1
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NVM_RC_VERSION=
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COLORTERM=truecolor
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HOMEBREW_PREFIX=/home/linuxbrew/.linuxbrew
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DESKTOP_SESSION=i3
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...
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PWD=/home/user
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LOGNAME=user
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MANPATH=/home/linuxbrew/.linuxbrew/share/man:
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XDG_SESSION_DESKTOP=i3
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XAUTHORITY=/run/user/1000/gdm/Xauthority
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WINDOWPATH=2
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SHELL=/bin/bash
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SSH_AGENT_PID=2900
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HOME=/home/user
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HOMEBREW_SHELLENV_PREFIX=/home/linuxbrew/.linuxbrew
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USERNAME=user
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$
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```
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Expected output:
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```console
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$ ./env-format.sh
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/home/user/Documents/public/sh/tests/student
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SHELL
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SSH_AGENT_PID
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HOMEBREW_SHELLENV_PREFIX
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MANPATH
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XAUTHORITY
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WINDOWPATH
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HOME
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$
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```
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### Hints
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Environment variables are variables that contain values necessary to set up a shell environment. Contrary to shell variables, environment variables persist in the shell’s child processes.
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```console
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VARIABLE_NAME=value
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```
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Most Common Environment Variables:
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- PWD – Current working directory.
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- HOME – The user’s home directory location.
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- SHELL – Current shell (bash, zsh, etc.).
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- LOGNAME – Name of the user.
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- UID – User’s unique identifier.
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- HOSTNAME – Device’s hostname on the network.
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- MAIL – User’s mail directory.
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- EDITOR – The Linux system default text editor.
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- TEMP – Directory location for temporary files.
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How to Check Environment Variables:
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Structurally, environment and shell variables are the same – both are a key-value pair, separated by an equal sign.
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- `printenv`. Prints the values of all or some environment variables.
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```console
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$ printenv HOME
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/home/user
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```
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Search Specific Environment Variables:
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To find all the variables containing a certain character or pattern, use the `grep` command:
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```console
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$ printenv | grep "W"
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HOMEBREW_PREFIX=/home/linuxbrew/.linuxbrew
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HOMEBREW_SHELLENV_PREFIX=/home/linuxbrew/.linuxbrew
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PWD=/home/user/Documents/
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WINDOWPATH=2
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OLDPWD=/home/user/Public
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```
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- awk. The awk command is a Linux tool and programming language that allows users to process and manipulate data and produce formatted reports.
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This flag will come in handy:
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`-F` [separator] Used to specify a file separator. The default separator is a blank space.
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```console
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$ cat example.txt
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Hello:my:name:is:John
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$ awk -F ":" '{print $5}' example.txt
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John
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$
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```
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> You have to use Man or Google to know more about commands flags, in order to solve this exercise!
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> Google and Man will be your friends!
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### References
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- [printenv](https://www.gnu.org/software/coreutils/manual/html_node/printenv-invocation.html#printenv-invocation).
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- [grep](https://www.gnu.org/software/grep/manual/grep.html).
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- [awk](https://www.ibm.com/docs/en/zos/2.4.0?topic=descriptions-awk-process-programs-written-in-awk-language)
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