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Unix tools

12-05-2024

Text files

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Count the lines in a file:

Awk:
```
  awk 'END {print NR}' file.txt
```
Grep:
```
  grep -c '^' file.txt
```
Sed:
```
  sed -n '$=' file.txt
```
Wc:
```
  wc -l file.txt
```

Filter by line

Print the first line of a file:

Awk:
```
  awk 'NR==1' file.txt
```
Head:
```
  head -n 1 file.txt
```
Sed:
```
  sed 1q file.txt
```
or:
```
  sed -n 1p file.txt
```

Print the first 10 lines of a file:

Awk:
```
  awk 'NR<=10' file.txt
```
Head:
```
  head -n 10 file.txt
```

Sed:

  sed 10q file.txt

or:

  sed -n 1,10p file.txt

Print the 5th line of a file:

Awk:
```
  awk 'NR==5' file.txt
```
Head:
```
  head -n 5 file.txt | tail -n 1
```

Sed:

  sed -n 5p file.txt

or:

  sed '5!d' file.txt

Print the last 10 lines of a file:

Sed:
```
  sed -e :a -e '$q;N;11,$D;ba' file.txt
```
Tail:
```
  tail -n 10 file.txt
```

Print the last line of a file:

Awk:
```
  awk 'END{print}' file.txt
```

Sed

  sed '$!d' file.txt

or:

  sed -n '$p' file.txt

Tail:
```
  tail -n 1 file.txt
```

Print a range of lines:

Awk:
```
  awk 'NR==8, NR==12' file.txt
```

Sed:

  sed '8,12!d' file.txt

or:

  sed -n 8,12p file.txt

Filter by regular expression

Print lines that match a regular expression:
- Awk:
```
  awk '/^#/' file.txt
```
- Grep:
```
  grep -E '^#' file.txt
```
Print lines that DO NOT match a regular expression:
- Awk:
```
  awk '!/^#|^$/' file.txt
```
- Grep:
```
  grep -vE '^#|^$' file.txt
```

Print next line after line matching a regular expression:

Awk:

  awk '/[Uu]nix/ {getline; print}' file.txt

Sed:
```
  sed -n '/[Uu]nix/ {n;p;}' file.txt
```

Print next 7 lines after line matching a regular expression:

Awk:

  awk -v l=7 '/[Uu]nix/ {for(i=l; i; --i) {getline; print}}' file.txt

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