diff options
| -rw-r--r-- | bash.html.markdown | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index 7ca4285b..11ce4e74 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -27,12 +27,12 @@ for the GNU operating system and as the default shell on most Linux distros. Nearly all examples below can be a part of a shell script or executed directly in the shell. -[Read more here.](http://www.gnu.org/software/bash/manual/bashref.html) +[Read more here.](https://www.gnu.org/software/bash/manual/bashref.html) ```bash #!/usr/bin/env bash # First line of the script is the shebang which tells the system how to execute -# the script: http://en.wikipedia.org/wiki/Shebang_(Unix) +# the script: https://en.wikipedia.org/wiki/Shebang_(Unix) # As you already figured, comments start with #. Shebang is also a comment. # Simple hello world example: @@ -198,7 +198,7 @@ then fi # Note that =~ only works within double [[ ]] square brackets, # which are subtly different from single [ ]. -# See http://www.gnu.org/software/bash/manual/bashref.html#Conditional-Constructs for more on this. +# See https://www.gnu.org/software/bash/manual/bashref.html#Conditional-Constructs for more on this. # Redefine command `ping` as alias to send only 5 packets alias ping='ping -c 5' @@ -325,6 +325,9 @@ echo "#helloworld" | tee output.out >/dev/null # WARNING: `rm` commands cannot be undone rm -v output.out error.err output-and-error.log rm -r tempDir/ # recursively delete +# You can install the `trash-cli` Python package to have `trash` +# which puts files in the system trash and doesn't delete them directly +# see https://pypi.org/project/trash-cli/ if you want to be careful # Commands can be substituted within other commands using $( ): # The following command displays the number of files and directories in the @@ -332,15 +335,15 @@ rm -r tempDir/ # recursively delete 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 $( ). +# 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 + # 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.";; + *) echo "It is not null.";; # match everything esac # `for` loops iterate for as many arguments given: @@ -377,6 +380,13 @@ do cat "$Output" done +# Bash can also accept patterns, like this to `cat` +# all the Markdown files in current directory +for Output in ./*.markdown +do + cat "$Output" +done + # while loop: while [ true ] do @@ -431,6 +441,8 @@ 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" @@ -448,7 +460,7 @@ grep -rI "^foo.*bar$" someDir/ # recursively `grep`, but ignore binary files grep "^foo.*bar$" file.txt | grep -v "baz" # if you literally want to search for the string, -# and not the regex, use fgrep (or grep -F) +# 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 @@ -457,6 +469,7 @@ fgrep "foobar" file.txt 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" |