mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 09:41:36 +00:00
282 lines
9.2 KiB
Markdown
282 lines
9.2 KiB
Markdown
|
---
|
|||
|
|
category: tool
|
|||
|
|
tool: bash
|
|||
|
|
contributors:
|
|||
|
|
- ["Max Yankov", "https://github.com/golergka"]
|
|||
|
|
- ["Darren Lin", "https://github.com/CogBear"]
|
|||
|
|
- ["Alexandre Medeiros", "http://alemedeiros.sdf.org"]
|
|||
|
|
- ["Denis Arh", "https://github.com/darh"]
|
|||
|
|
- ["akirahirose", "https://twitter.com/akirahirose"]
|
|||
|
|
- ["Anton Strömkvist", "http://lutic.org/"]
|
|||
|
|
- ["Rahil Momin", "https://github.com/iamrahil"]
|
|||
|
|
- ["Gregrory Kielian", "https://github.com/gskielian"]
|
|||
|
|
- ["Etan Reisner", "https://github.com/deryni"]
|
|||
|
|
filename: LearnBash.sh
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
Bash это командная оболочка unix (unix shell), которая распространяется как оболочка для операционной системы GNU и используется в качестве оболочки по умолчанию для Linux и Mac OS X.
|
|||
|
|
Почти все нижеприведенные примеры могут могут быть частью shell-скриптов или быть исполнены напрямую в shell.
|
|||
|
|
|
|||
|
|
[Подробнее.](http://www.gnu.org/software/bash/manual/bashref.html)
|
|||
|
|
|
|||
|
|
```bash
|
|||
|
|
#!/bin/bash
|
|||
|
|
# Первая строка скрипта - это shebang, который сообщает системе как испольнять
|
|||
|
|
# этот скрипт: http://en.wikipedia.org/wiki/Shebang_(Unix)
|
|||
|
|
# Как вы уже поняли, комментарии начинаются с #. Shebang - это тоже коммантарий.
|
|||
|
|
|
|||
|
|
# Простой пример hello world:
|
|||
|
|
echo Hello world!
|
|||
|
|
|
|||
|
|
# Отдельные команды начинаются с новой строки или разделяются точкой с запятой:
|
|||
|
|
echo 'This is the first line'; echo 'This is the second line'
|
|||
|
|
|
|||
|
|
# Вот так объявляется пемеренная:
|
|||
|
|
VARIABLE="Some string"
|
|||
|
|
|
|||
|
|
# Но не так:
|
|||
|
|
VARIABLE = "Some string"
|
|||
|
|
# Bash решит что VARIABLE - это команда, которую он должен исполнить,
|
|||
|
|
# и выдаст ошибку, потому что не сможет найти ее.
|
|||
|
|
|
|||
|
|
# И не так:
|
|||
|
|
VARIABLE= 'Some string'
|
|||
|
|
# Тут Bash решит что 'Some string' - это команда, которую он должен исполнить,
|
|||
|
|
# и выдаст ошибку, потому что не сможет найти ее (здесь 'VARIABLE=' выглядит
|
|||
|
|
# как присвоение значения переменной, но только в контексте исполнения
|
|||
|
|
# команды 'Some string').
|
|||
|
|
|
|||
|
|
# Использование переменой:
|
|||
|
|
echo $VARIABLE
|
|||
|
|
echo "$VARIABLE"
|
|||
|
|
echo '$VARIABLE'
|
|||
|
|
# Когда вы используете переменную — присвоение, экспорт и т.д — вы пищете её
|
|||
|
|
# имя без $. А для получения значения переменной, используйте $.
|
|||
|
|
# Заметте что ' (одинарные кавычки) не раскрывают переменные в них.
|
|||
|
|
|
|||
|
|
# Подстановка строк в переменных
|
|||
|
|
echo ${VARIABLE/Some/A}
|
|||
|
|
# Это выражение заменит первую встреченную подстроку "Some" на "A"
|
|||
|
|
|
|||
|
|
# Подстановка из переменной
|
|||
|
|
LENGTH=7
|
|||
|
|
echo ${VARIABLE:0:LENGTH}
|
|||
|
|
# This will return only the first 7 characters of the value
|
|||
|
|
|
|||
|
|
# Default value for variable
|
|||
|
|
echo ${FOO:-"DefaultValueIfFOOIsMissingOrEmpty"}
|
|||
|
|
# This works for null (FOO=), empty string (FOO=""), zero (FOO=0) returns 0
|
|||
|
|
|
|||
|
|
# Builtin variables:
|
|||
|
|
# There are some useful builtin variables, like
|
|||
|
|
echo "Last program return value: $?"
|
|||
|
|
echo "Script's PID: $$"
|
|||
|
|
echo "Number of arguments: $#"
|
|||
|
|
echo "Scripts arguments: $@"
|
|||
|
|
echo "Scripts arguments seperated in different variables: $1 $2..."
|
|||
|
|
|
|||
|
|
# Reading a value from input:
|
|||
|
|
echo "What's your name?"
|
|||
|
|
read NAME # Note that we didn't need to declare a new variable
|
|||
|
|
echo Hello, $NAME!
|
|||
|
|
|
|||
|
|
# We have the usual if structure:
|
|||
|
|
# use 'man test' for more info about conditionals
|
|||
|
|
if [ $NAME -ne $USER ]
|
|||
|
|
then
|
|||
|
|
echo "Your name isn't your username"
|
|||
|
|
else
|
|||
|
|
echo "Your name is your username"
|
|||
|
|
fi
|
|||
|
|
|
|||
|
|
# There is also conditional execution
|
|||
|
|
echo "Always executed" || echo "Only executed if first command fails"
|
|||
|
|
echo "Always executed" && echo "Only executed if first command does NOT fail"
|
|||
|
|
|
|||
|
|
# To use && and || with if statements, you need multiple pairs of square brackets:
|
|||
|
|
if [ $NAME == "Steve" ] && [ $AGE -eq 15 ]
|
|||
|
|
then
|
|||
|
|
echo "This will run if $NAME is Steve AND $AGE is 15."
|
|||
|
|
fi
|
|||
|
|
|
|||
|
|
if [ $NAME == "Daniya" ] || [ $NAME == "Zach" ]
|
|||
|
|
then
|
|||
|
|
echo "This will run if $NAME is Daniya OR Zach."
|
|||
|
|
fi
|
|||
|
|
|
|||
|
|
# Expressions are denoted with the following format:
|
|||
|
|
echo $(( 10 + 5 ))
|
|||
|
|
|
|||
|
|
# Unlike other programming languages, bash is a shell — so it works in a context
|
|||
|
|
# of current directory. You can list files and directories in the current
|
|||
|
|
# directory with the ls command:
|
|||
|
|
ls
|
|||
|
|
|
|||
|
|
# These commands have options that control their execution:
|
|||
|
|
ls -l # Lists every file and directory on a separate line
|
|||
|
|
|
|||
|
|
# Results of the previous command can be passed to the next command as input.
|
|||
|
|
# grep command filters the input with provided patterns. That's how we can list
|
|||
|
|
# .txt files in the current directory:
|
|||
|
|
ls -l | grep "\.txt"
|
|||
|
|
|
|||
|
|
# You can redirect command input and output (stdin, stdout, and stderr).
|
|||
|
|
# Read from stdin until ^EOF$ and overwrite hello.py with the lines
|
|||
|
|
# between "EOF":
|
|||
|
|
cat > hello.py << EOF
|
|||
|
|
#!/usr/bin/env python
|
|||
|
|
from __future__ import print_function
|
|||
|
|
import sys
|
|||
|
|
print("#stdout", file=sys.stdout)
|
|||
|
|
print("#stderr", file=sys.stderr)
|
|||
|
|
for line in sys.stdin:
|
|||
|
|
print(line, file=sys.stdout)
|
|||
|
|
EOF
|
|||
|
|
|
|||
|
|
# Run hello.py with various stdin, stdout, and stderr redirections:
|
|||
|
|
python hello.py < "input.in"
|
|||
|
|
python hello.py > "output.out"
|
|||
|
|
python hello.py 2> "error.err"
|
|||
|
|
python hello.py > "output-and-error.log" 2>&1
|
|||
|
|
python hello.py > /dev/null 2>&1
|
|||
|
|
# The output error will overwrite the file if it exists,
|
|||
|
|
# if you want to append instead, use ">>":
|
|||
|
|
python hello.py >> "output.out" 2>> "error.err"
|
|||
|
|
|
|||
|
|
# Overwrite output.txt, append to error.err, and count lines:
|
|||
|
|
info bash 'Basic Shell Features' 'Redirections' > output.out 2>> error.err
|
|||
|
|
wc -l output.out error.err
|
|||
|
|
|
|||
|
|
# Run a command and print its file descriptor (e.g. /dev/fd/123)
|
|||
|
|
# see: man fd
|
|||
|
|
echo <(echo "#helloworld")
|
|||
|
|
|
|||
|
|
# Overwrite output.txt with "#helloworld":
|
|||
|
|
cat > output.out <(echo "#helloworld")
|
|||
|
|
echo "#helloworld" > output.out
|
|||
|
|
echo "#helloworld" | cat > output.out
|
|||
|
|
echo "#helloworld" | tee output.out >/dev/null
|
|||
|
|
|
|||
|
|
# Cleanup temporary files verbosely (add '-i' for interactive)
|
|||
|
|
rm -v output.out error.err output-and-error.log
|
|||
|
|
|
|||
|
|
# Commands can be substituted within other commands using $( ):
|
|||
|
|
# The following command displays the number of files and directories in the
|
|||
|
|
# current directory.
|
|||
|
|
echo "There are $(ls | wc -l) items here."
|
|||
|
|
|
|||
|
|
# The same can be done using backticks `` but they can't be nested - the preferred way
|
|||
|
|
# is to use $( ).
|
|||
|
|
echo "There are `ls | wc -l` items here."
|
|||
|
|
|
|||
|
|
# Bash uses a case statement that works similarly to switch in Java and C++:
|
|||
|
|
case "$VARIABLE" in
|
|||
|
|
#List patterns for the conditions you want to meet
|
|||
|
|
0) echo "There is a zero.";;
|
|||
|
|
1) echo "There is a one.";;
|
|||
|
|
*) echo "It is not null.";;
|
|||
|
|
esac
|
|||
|
|
|
|||
|
|
# for loops iterate for as many arguments given:
|
|||
|
|
# The contents of $VARIABLE is printed three times.
|
|||
|
|
for VARIABLE in {1..3}
|
|||
|
|
do
|
|||
|
|
echo "$VARIABLE"
|
|||
|
|
done
|
|||
|
|
|
|||
|
|
# Or write it the "traditional for loop" way:
|
|||
|
|
for ((a=1; a <= 3; a++))
|
|||
|
|
do
|
|||
|
|
echo $a
|
|||
|
|
done
|
|||
|
|
|
|||
|
|
# They can also be used to act on files..
|
|||
|
|
# This will run the command 'cat' on file1 and file2
|
|||
|
|
for VARIABLE in file1 file2
|
|||
|
|
do
|
|||
|
|
cat "$VARIABLE"
|
|||
|
|
done
|
|||
|
|
|
|||
|
|
# ..or the output from a command
|
|||
|
|
# This will cat the output from ls.
|
|||
|
|
for OUTPUT in $(ls)
|
|||
|
|
do
|
|||
|
|
cat "$OUTPUT"
|
|||
|
|
done
|
|||
|
|
|
|||
|
|
# while loop:
|
|||
|
|
while [ true ]
|
|||
|
|
do
|
|||
|
|
echo "loop body here..."
|
|||
|
|
break
|
|||
|
|
done
|
|||
|
|
|
|||
|
|
# You can also define functions
|
|||
|
|
# Definition:
|
|||
|
|
function foo ()
|
|||
|
|
{
|
|||
|
|
echo "Arguments work just like script arguments: $@"
|
|||
|
|
echo "And: $1 $2..."
|
|||
|
|
echo "This is a function"
|
|||
|
|
return 0
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
# or simply
|
|||
|
|
bar ()
|
|||
|
|
{
|
|||
|
|
echo "Another way to declare functions!"
|
|||
|
|
return 0
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
# Calling your function
|
|||
|
|
foo "My name is" $NAME
|
|||
|
|
|
|||
|
|
# There are a lot of useful commands you should learn:
|
|||
|
|
# prints last 10 lines of file.txt
|
|||
|
|
tail -n 10 file.txt
|
|||
|
|
# prints first 10 lines of file.txt
|
|||
|
|
head -n 10 file.txt
|
|||
|
|
# sort file.txt's lines
|
|||
|
|
sort file.txt
|
|||
|
|
# report or omit repeated lines, with -d it reports them
|
|||
|
|
uniq -d file.txt
|
|||
|
|
# prints only the first column before the ',' character
|
|||
|
|
cut -d ',' -f 1 file.txt
|
|||
|
|
# replaces every occurrence of 'okay' with 'great' in file.txt, (regex compatible)
|
|||
|
|
sed -i 's/okay/great/g' file.txt
|
|||
|
|
# print to stdout all lines of file.txt which match some regex
|
|||
|
|
# The example prints lines which begin with "foo" and end in "bar"
|
|||
|
|
grep "^foo.*bar$" file.txt
|
|||
|
|
# pass the option "-c" to instead print the number of lines matching the regex
|
|||
|
|
grep -c "^foo.*bar$" file.txt
|
|||
|
|
# if you literally want to search for the string,
|
|||
|
|
# and not the regex, use fgrep (or grep -F)
|
|||
|
|
fgrep "^foo.*bar$" file.txt
|
|||
|
|
|
|||
|
|
|
|||
|
|
# Read Bash shell builtins documentation with the bash 'help' builtin:
|
|||
|
|
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
|
|||
|
|
```
|