Bash long string, no word splitting?

bash shell shell-script command-line zsh

6,010

Solution 1

Using line continuations like that adds spaces into your string: the sequence backslash-newline-whitespace will be replaced by a single space.

Just using a variables will go a long way towards improved readability:

url="reallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallyreallylongstring"
{ somecheck || somecomand "$url" } &> /dev/null &

You can still break that up into substrings, using an array

parts=(
    "reallyreallyreallyreally"
    "reallyreallyreallyreally"
    "reallyreallyreallyreally"
    "reallyreallyreallyreally"
    "longstring"
)
whole=$(IFS=; echo "${parts[*]}")

but is it that important to split up literal strings given the added complexity?

Solution 2

Well, you could simplify it slightly to:

$ [ -f /dev/null ] || sed 's/a/A/g' <(echo "thisis""avery"\
"long""string"\
"Ihave""separated"\
"into""smaller"\
"substrings")
thisisAverylongstringIhAvesepArAtedintosmAllersubstrings

The important point is to not have any extra whitespace in the input string, so no spaces around the \.

Glenn's suggestion to use variables is both prettier and simpler though, go with that.

6,010

ferhtgoldaraz

Updated on September 18, 2022

Comments

ferhtgoldaraz over 1 year
I want to tidy up some script with long commands, so that for example:
```
{ somecheck || somecomand "reallyreallyreallyreallyreallyreallylongstring" } &> /dev/null &
```
becomes something like:
```
{ somecheck ||                   \
    somecomand "reallyreally"    \
        "reallyreally"           \
        "reallyreally"           \
        "longstring"             \
} &> /dev/null &
```
But I'm worried about word splitting. To avoid it, I'm considering this:
```
{ somecheck ||                   \
    somecomand  "$(echo          \
        "reallyreally"           \
        "reallyreally"           \
        "reallyreally"           \
        "longstring"             \
    )"                           \
} &> /dev/null &
```
Does any one know some other way to do multiline strings in bash/zsh? I'm having trouble googling for this info, and I think this'll mean at least three processes (the script, the background block, and the command substitution subshell); Maybe there's a better way?

Thanks in advance!
- terdon about 9 years
  
  Just to clarify, you don't actually want multiline strings right? The whole issue is to not include the newlines in the string but use them only for readability, is that correct?
- ferhtgoldaraz about 9 years
  
  Yes, the string could be for example an URL
- Overmind Jiang about 9 years
  
  How long is "really long"? At work, we have a program where the command line (which is mostly machine-generated) is encroaching on a 128 KiB limit, and of the nearly 200 arguments, one is over 100 KiB. That's extremely long by any reasonable definition. It's hard to copy'n'paste that for analysis.
- ferhtgoldaraz about 9 years
  
  Arbitrarily long, though my use cases are not that extreme
Angel Todorov about 9 years

Make sure you quote your "$vars" unless you want word splitting and filename generation on the values.
Angel Todorov about 9 years

yes += works with bash for appending strings.