diff options
Diffstat (limited to 'bash.html.markdown')
| -rw-r--r-- | bash.html.markdown | 66 | 
1 files changed, 34 insertions, 32 deletions
| diff --git a/bash.html.markdown b/bash.html.markdown index e0c12f97..08182c2c 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -32,39 +32,41 @@ echo Hello world!  echo 'This is the first line'; echo 'This is the second line'  # Declaring a variable looks like this: -VARIABLE="Some string" +Variable="Some string"  # But not like this: -VARIABLE = "Some string" -# Bash will decide that VARIABLE is a command it must execute and give an error +Variable = "Some string" +# Bash will decide that Variable is a command it must execute and give an error  # because it can't be found.  # Or like this: -VARIABLE= 'Some string' +Variable= 'Some string'  # Bash will decide that 'Some string' is a command it must execute and give an -# error because it can't be found. (In this case the 'VARIABLE=' part is seen +# error because it can't be found. (In this case the 'Variable=' part is seen  # as a variable assignment valid only for the scope of the 'Some string'  # command.)  # Using the variable: -echo $VARIABLE -echo "$VARIABLE" -echo '$VARIABLE' +echo $Variable +echo "$Variable" +echo '$Variable'  # When you use the variable itself — assign it, export it, or else — you write  # its name without $. If you want to use variable's value, you should use $.  # Note that ' (single quote) won't expand the variables!  # String substitution in variables -echo ${VARIABLE/Some/A} -# This will substitute the first occurance of "Some" with "A" +echo ${Variable/Some/A} +# This will substitute the first occurrence of "Some" with "A"  # Substring from a variable -echo ${VARIABLE:0:7} +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 +echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"} +# This works for null (Foo=) and empty string (Foo=""); zero (Foo=0) returns 0. +# Note that it only returns default value and doesn't change variable value.  # Builtin variables:  # There are some useful builtin variables, like @@ -72,16 +74,16 @@ 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..." +echo "Scripts arguments separated 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! +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 ] +if [ $Name -ne $USER ]  then      echo "Your name isn't your username"  else @@ -93,14 +95,14 @@ 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 ] +if [ $Name == "Steve" ] && [ $Age -eq 15 ]  then -    echo "This will run if $NAME is Steve AND $AGE is 15." +    echo "This will run if $Name is Steve AND $Age is 15."  fi -if [ $NAME == "Daniya" ] || [ $NAME == "Zach" ] +if [ $Name == "Daniya" ] || [ $Name == "Zach" ]  then -    echo "This will run if $NAME is Daniya OR Zach." +    echo "This will run if $Name is Daniya OR Zach."  fi  # Expressions are denoted with the following format: @@ -142,7 +144,7 @@ python hello.py > /dev/null 2>&1  # 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: +# Overwrite output.out, append to error.err, and count lines:  info bash 'Basic Shell Features' 'Redirections' > output.out 2>> error.err  wc -l output.out error.err @@ -150,7 +152,7 @@ wc -l output.out error.err  # see: man fd  echo <(echo "#helloworld") -# Overwrite output.txt with "#helloworld": +# Overwrite output.out with "#helloworld":  cat > output.out <(echo "#helloworld")  echo "#helloworld" > output.out  echo "#helloworld" | cat > output.out @@ -169,7 +171,7 @@ echo "There are $(ls | wc -l) items here."  echo "There are `ls | wc -l` items here."  # Bash uses a case statement that works similarly to switch in Java and C++: -case "$VARIABLE" in  +case "$Variable" in      #List patterns for the conditions you want to meet      0) echo "There is a zero.";;      1) echo "There is a one.";; @@ -177,10 +179,10 @@ case "$VARIABLE" in  esac  # for loops iterate for as many arguments given: -# The contents of $VARIABLE is printed three times. -for VARIABLE in {1..3} +# The contents of $Variable is printed three times. +for Variable in {1..3}  do -    echo "$VARIABLE" +    echo "$Variable"  done  # Or write it the "traditional for loop" way: @@ -191,16 +193,16 @@ done  # They can also be used to act on files..  # This will run the command 'cat' on file1 and file2 -for VARIABLE in file1 file2 +for Variable in file1 file2  do -    cat "$VARIABLE" +    cat "$Variable"  done  # ..or the output from a command  # This will cat the output from ls. -for OUTPUT in $(ls) +for Output in $(ls)  do -    cat "$OUTPUT" +    cat "$Output"  done  # while loop: @@ -228,7 +230,7 @@ bar ()  }  # Calling your function -foo "My name is" $NAME +foo "My name is" $Name  # There are a lot of useful commands you should learn:  # prints last 10 lines of file.txt | 
