Command line tricks: manipulate texts: Westerlies — a memex

Command line tricks: manipulate texts

Command line tools: sed, awk.

Results will be printed instead of being saved to the original file (add -i if needed)

Print text

print the 1st and 3rd line of the file

sed -n '1,3p' file # using sed
cat file | awk '{ print $1 $3 }' # using awk

print the lines that contain "text"
```
sed -n '/text/p' file.txt
```

print the last line and its line number

sed -n '$p;$=' file # using sed
awk 'END{print NR; print }' file # using awk

print even lines
```
sed -n 'n;p' file
```
print odd lines
```
sed -n 'p;n' file
```
print the first column with separator -
```
awk -F- '{print $1}' file
```
print the 4th and the last columns
```
awk '{ print $4, $NF}' file
```

Replace text

replace all the "test" with "test2", starting at the line N
```
sed 's/test/test2/Ng' file
```
Find all the words, replace them with [word]
```
sed -n 's/\w\+/[&]/gp'
```

Insert text

insert 'new line' before all the lines that start with 'test'
```
sed '/^test/i\new line` file
```
insert 'new line' after all the lines that start with 'test'
```
sed '/^test/a\new line` file
```
insert a prefix string to the begining of each line
```
sed -e 's/^/prefix/' file > newfile
```
insert a prefix string to the end of each line
```
sed -e 's/$/prefix/' file > newfile
```
insert "text" before the 10th line
```
sed '10 i\text' input.txt
```

Delete text

delete all the lines from the 2nd line to the last line
```
sed '2,$d' file
```
delete lines 2-5 and line 10
```
sed -e '2,5d;10d' file
```

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