Iterating through grep results line by line not delimited by space

Question

I'm using a bash script to identify where something is used and then find a corresponding reference (name). The script is: ``` #!/bin/bash echo "running, searching for instances of ${1:0:1}/$1" for i in ls -d Module*; do if [ -d "$i" ]; then if [ -f $i/003.Design/003.Data.efx ]; then if grep -qe "Module-0000/003.Design/005.Types/${1:0:1}/$1" $i/003.Design/003.Data.efx; then echo $i $i/003.Design/003.Data.efx grep -B 4 "Module-0000/003.Design/005.Types/${1:0:1}/$1" $i/003.Design/003.Data.efx | grep "name" fi fi fi done ``` I'm trying to change it to: ``` #!/bin/bash echo "running, searching for instances of ${1:0:1}/$1" for i in ls -d Module*; do if [ -d "$i" ]; then if [ -f $i/003.Design/003.Data.efx ]; then if grep -qe "Module-0000/003.Design/005.Types/${1:0:1}/$1" $i/003.Design/003.Data.efx; then echo $i $i/003.Design/003.Data.efx for j in `grep -B 4 "Module-0000/003.Design/005.Types/${1:0:1}/$1" $i/003.Design/003.Data.efx | grep "name"` ; do echo $j done fi fi fi done ``` When I ma…

Accepted Answer

tl;dr:

- Change `for i in ls -d Module*; do` to `for i in Module*/;do`

- Replace

```
for j in `grep -B 4 "Module-0000/003.Design/005.Types/${1:0:1}/$1" $i/003.Design/003.Data.efx | grep "name"` ; do
  echo $j
done
```

with

```
while IFS= read -r j; do 
  echo "$j"
done < <(grep -B 4 "Module-0000/003.Design/005.Types/${1:0:1}/$1" "$i/003.Design/003.Data.efx" | grep "name")
```

See below for a full discussion.

`for i in ls -d Module*; do` will simply enumerate tokens `ls`, `-d` and (possibly expanded) `Module*` instead of enumerating the output from an `ls` command.

To correct that immediate problem, you'd have to use command substitution (`for i in $(ls -d Module*; do)`), but that is not advisable, because using globbing (pathname expansion) directly is the robust, proper solution: `for i in Module*/; do`

Similarly, it's not advisable to use a `for` loop to parse command output line by line, because the output is subject to word splitting, among other shell expansions. Effectively, the `for` loop enumerates whitespace-separated tokens rather than full lines.

Using a `while` loop with `IFS= read -r`, with input provided via process substitution, is the right approach - it ensures that lines are read unmodified.

Also, it's generally advisable to double-quote variable references to avoid unwanted shell expansions.

A revised form of your code is therefore:

```
shopt -s nullglob  # ensure that a glob matching nothing expands to empty string
for i in Module*/; do 
  if [[ -f "$i/003.Design/003.Data.efx" ]]; then
    if grep -qe "Module-0000/003.Design/005.Types/${1:0:1}/$1" "$i/003.Design/003.Data.efx"; then
      echo "$i $i/003.Design/003.Data.efx"
      while IFS= read -r j; do 
        echo "$j"
      done < <(grep -B 4 "Module-0000/003.Design/005.Types/${1:0:1}/$1" "$i/003.Design/003.Data.efx" | grep "name")
    fi
  fi
done
```

Iterating through grep results line by line not delimited by space

Solution

Problem