Limit Strings

A heredoc uses the limitstring to determine when to stop consuming input. The terminating limitstring must

Be at the start of a line.
Be the only text on the line Note: If you use <<- the limitstring can be prefixed with tabs \t

Correct:

cat <<limitstring
line 1
line 2
limitstring

This will output:

``` line 1 line 2

Incorrect use:

cat <<limitstring line 1 line 2 limitstring

Since `limitstring` on the last line is not exactly at the start of the line, the shell will continue to wait for further input, until it sees a line that starts with `limitstring` and doesn’t contain anything else. Only then it will stop waiting for input, and proceed to pass the here-document to the `cat` command.

Note that when you prefix the initial limitstring with a hyphen, any tabs at the start of the line are removed before parsing, so the data and the limit string can be indented with tabs (for ease of reading in shell scripts).

cat <<-limitstring line 1 has a tab each before the words line and has line 2 has two leading tabs limitstring

will produce

> ```
line 1    has a tab each before the words line and has
line 2 has two leading tabs

with the leading tabs (but not the internal tabs) removed.

Found a mistake? Have a question or improvement idea? Let me know.

Here documents and here strings/

Here documents and here strings

Execute command with here document

Indenting here documents

Here strings

Create a file

Run several commands with sudo

Limit Strings

Table Of Contents

1 Getting started

2 Using trap to react to signals and system events

3 Listing files

4 Aliasing

5 Jobs and processes

6 Redirection

7 Control structures

8 Using cat

9 Arrays

10 Functions

11 Bash Parameter Expansion

12 Sourcing

13 Find

14 Here documents and here strings

15 Quoting

16 Conditional Expressions

17 Scripting with parameters

18 History substitutions

19 Math

20 Scoping

21 Process substitution

22 Programmable completion

23 Customizing PS1

24 Brace Expansion

25 Bash Arithmetic

26 getopts smart positional-parameter parsing

27 Debugging

28 Pitfalls

29 Script shebang

30 Pattern matching and regular expressions

31 Keyboard shortcuts

32 Change shell

33 Copying with cp

34 Internal variables

35 Job control

36 Case statement

37 Word splitting

38 Read a file

39 File transfer with scp

40 Pipelines

41 Managing PATH environment variable

42 Avoiding date using printf

43 Chain of commands and operations

44 Type of shells

45 true, false and commands

46 Color script output cross-platform

47 Navigating directories

48 Using sort

49 Namespace

50 co-processes

51 Typing variables

52 Jobs at specific types

53 Associative arrays

54 Handling the system prompt

55 Creating directories

56 File execution sequence

57 The cut command

58 Bash on Windows 10

59 Cut command

60 Splitting files

61 Global and local variables

62 Design Patterns

63 CGI Scripts

64 Select keyword

65 When to use eval

66 Networking with bash

67 Parallel

68 Grep

69 Strace

70 Sleep

71 Decodi

72 Contributors