БАШ

Bash — это название оболочки Unix, которая также распространялась как оболочка для операционной системы GNU и как оболочка по умолчанию в большинстве искажений Linux. Почти все приведенные ниже примеры могут быть частью сценария оболочки или выполняться непосредственно в оболочке.

first line of the script is the shebang which tells the system how to execute: !/usr/bin/env bash
simple example hello world: echo hello world
#Declaring a variable look like this:
Variable= “some string”
echo $variable → some string
echo “$variable” → some variable
echo ‘$variable’ → $variable
Parameter expansion:
echo ${Variable} → some string. this is a simple use of parameter expansion. parameter expansion gets a value from a variable. it “expands” or prints the value. During the expansion time the value or parameter can be modified.
string substitution in variables:
echo ${variable/some/A} → this will substitute the first occurence of “some” with “A”.
length=7 → echo ${variable:0:length} this will return only the first 7 characters of the value.
array0=(one two three five) → declare an array with 5 elements.
echo $array0
echo ${array0[0]}
|| for i in “${array0[@]}”; do
echo “$i”
done|| → print all elements . each of them on new line.
echo “ i’m in $(pwd)” → execs pwd and interpolates output.
echo “i’m in $PWD” → interpolates the variable
|| if [ $name! =$USER]
then
echo “your name isn’t your username”
else
echo “your name is your username” || → we have the usual IF structure. use ‘man test’ for more info about conditional. true if the value of $name is not equal to the current user’s login username.
alias ping = ‘ping -c 5’ → redefine command ‘ping’ as alias to send only 5 packets.
\ping 192.168.1.1 → Escape the alias and use command with this name instead
# You can also define functions
# Definition:
function foo ()
{
    echo "Arguments work just like script arguments: $@"
    echo "And: $1 $2..."
    echo "This is a function"
    returnValue=0    # Variable values can be returned
    return $returnValue
}
# Call the function `foo` with two arguments, arg1 and arg2:
foo arg1 arg2
# => Arguments work just like script arguments: arg1 arg2
# => And: arg1 arg2...
# => This is a function
# Return values can be obtained with $?
resultValue=$?
# More than 9 arguments are also possible by using braces, e.g. ${10}, ${11}, ...

# or simply
bar ()
{
    echo "Another way to declare functions!"
    return 0
}
# Call the function `bar` with no arguments:
bar # => Another way to declare functions!

# Calling your function
foo "My name is" $Name

# There are a lot of useful commands you should learn:
# prints last 10 lines of file.txt
tail -n 10 file.txt

# prints first 10 lines of file.txt
head -n 10 file.txt

# sort file.txt's lines
sort file.txt

# report or omit repeated lines, with -d it reports them
uniq -d file.txt

# prints only the first column before the ',' character
cut -d ',' -f 1 file.txt

# replaces every occurrence of 'okay' with 'great' in file.txt
# (regex compatible)
sed -i 's/okay/great/g' file.txt
# be aware that this -i flag means that file.txt will be changed
# -i or --in-place erase the input file (use --in-place=.backup to keep a back-up)

# print to stdout all lines of file.txt which match some regex
# The example prints lines which begin with "foo" and end in "bar"
grep "^foo.*bar$" file.txt

# pass the option "-c" to instead print the number of lines matching the regex
grep -c "^foo.*bar$" file.txt

# Other useful options are:
grep -r "^foo.*bar$" someDir/ # recursively `grep`
grep -n "^foo.*bar$" file.txt # give line numbers
grep -rI "^foo.*bar$" someDir/ # recursively `grep`, but ignore binary files

# perform the same initial search, but filter out the lines containing "baz"
grep "^foo.*bar$" file.txt | grep -v "baz"

# if you literally want to search for the string,
# and not the regex, use `fgrep` (or `grep -F`)
fgrep "foobar" file.txt

# The `trap` command allows you to execute a command whenever your script
# receives a signal. Here, `trap` will execute `rm` if it receives any of the
# three listed signals.
trap "rm $TEMP_FILE; exit" SIGHUP SIGINT SIGTERM

# `sudo` is used to perform commands as the superuser
# usually it will ask interactively the password of superuser
NAME1=$(whoami)
NAME2=$(sudo whoami)
echo "Was $NAME1, then became more powerful $NAME2"

# Read Bash shell built-ins documentation with the bash `help` built-in:
help
help help
help for
help return
help source
help .

# Read Bash manpage documentation with `man`
apropos bash
man 1 bash
man bash

# Read info documentation with `info` (`?` for help)
apropos info | grep '^info.*('
man info
info info
info 5 info

# Read bash info documentation:
info bash
info bash 'Bash Features'
info bash 6
info --apropos bash

СПАСИБО…. !!