echo
1
echo "Hello World with new line"
1
echo -n "Hello World without new line"
while
1
2
3
4
5
6
while [ $bool ] do
# ...Code...
done
for
1
2
3
4
5
for (( i = 0; i < 10; i++ )) do
# ...Code...
done
if
1
2
3
4
5
6
7
if [ $bool ] ; then
# Do something
elif [ $other_bool ] ; then
# Do something else
else
# Do something else
fi
Take input
1
2
read a
echo $a
Arguments
Number of arguments: $#
Nth Argument: $n (n = [1-9])
Functions
1
2
3
function name(){
}
Read a file
1
2
3
4
5
6
file="book.txt"
while read line; do
echo $line
done < $file
Read a directory
1
2
3
for i in [dir]/* ; do
echo "$i"
done
if tests
1
2
3
4
5
6
7
8
9
10
11
12
13
arg = $1
if [ -e $arg ] ; then
echo "$arg exists"
fi
if [ -f $arg ] ; then
echo "$arg is a file"
elif [ -d $arg ] ; then
echo "$arg is a directory"
else
echo "$arg is something else"
fi
1
2
3
4
5
6
7
8
if [ $# -ne 1 ] ; then
echo "I need only one argument" 1>&2
exit 1;
fi
if [ ! -f $1 ] ; then
echo "Argument is not a file" 1>&2
exit 2;
sleep
1
2
3
echo "Wait for 5 seconds"
sleep 5
echo "Done"
cut
cut -d [seperation_character] -f[field_num]
1
cut -d " " -f1
sort
[expression] sort -k[num] -t [char]
Sort the lines of the output of the [expression] based on the [num] field after sererating them based on the [char]
uniq
Before uniq always sort
Removes concurrent duplicate lines
-c adds a prefix of the number of occurences
1
ls | sort | uniq -c
tr
- tr [first_set] [second_set]
Replaces the first set of characters with the second one
1
tr [:lower:] [:upper:]
- tr -s [character]
Replace each sequence of a repeated character that is listed in the last specified SET, with a single occurrence of that character
1
tr -s " "
Inline code
a=[command]
The result of the [command] goes into the variable a
head
| [expression] | head -n[num] |
Print the first [num] of lines of the [expression]’s output
tail
| [expression] | tail -n[num] |
Print the last [num] of lines of the [expression]’s output
Error message
echo [message] 1>&2; exit [num!=0]
1
2
3
4
if [ $# -ne 1 ] ; then
echo "One argument needed" 1>&2;
exit 1
fi
egrep
egrep [options] PATTERN [FILE…]
Options
-v reverse of the pattern
--color adds color to matches
-c count the number of matches
-i ignores case