Strange behavior using read for validate string (bash script)

Question

I are creating a .sh using bash for validate the api sub folders versions

The objective is validate this strings into APIS_BUILD var and find all .proto files into ./proto folder to compile into protobuffer Go file

# define subfolder apis to build
APIS_BUILD=(
    prototests/v1/
    prototests2/v2
    testfolder
)
# the "testfolder" are a invalid folder

Test cases:

prototestes/v1                      # valid
prototestes/v1/cobranca             # valid
prototestes/v1/cobrnaca/faturamento # valid
outrapastacomarquivosproto/v1       # valid
prototests                          # invalid
/prototests                         # invalid

Then, I created this script for validate the APIS_BUILD string array

#!/usr/bin/env bash

# text color
RED='\033[0;31m'  # RED
BLUE='\033[0;34m' # Blue
NC='\033[0m'      # No Color

# Underline color
UCyan='\033[4;36m' # Cyan

# define subfolder apis to build
APIS_BUILD=(
    prototests/v1
    cobrancas/v1
)
DST_DIR="."       # define the directory to store the build-in protofiles
SRC_DIR="./proto" # define the proto files folder

# Compile proto file
# $1 = Filename to compile
function compile() {
    protoc --go_out=$DST_DIR --proto_path=proto --go_opt=M$1=services \
        --go_opt=paths=import --go-grpc_out=. \
        $1
}

# Validate api_build's
function validateApiBuilds() {
    for t in ${APIS_BUILD[@]}; do
        IFS="/"
        read -a SUBSTR <<<"$t"
        if [ ${#SUBSTR[@]} -lt 2 ]; then
            printf "${RED}The API_BUILD value ${UCyan}\"${t}\"${RED} are declare wrong, please declare [api_folder]/[version_folder] (example: prototest/v1)${NC}\n" 1>&2
            exit 1
        fi
    done
}

validateApiBuilds

for filename in $(find $SRC_DIR -name '*.proto'); do
    [ -e "$filename" ] || continue
    echo $filename
done

The subfolder:

But I getting a strange behavior:

If run the .sh file with the validateApiBuilds function the return for $filename is always .
If run the .sh file without the validateApiBuilds function the return for $filename are getting the testservice.proto file

Pictures:

With validateApiBuilds function:

Without validateApiBuilds function:

All the variables:

# define subfolder apis to build
APIS_BUILD=(
    prototests/v1
    cobrancas/v1
)
DST_DIR="."       # define the directory to store the build-in protofiles
SRC_DIR="./proto" # define the proto files folder

Bash version:

$ bash --version                                  
$ GNU bash, versão 4.4.19(1)-release (x86_64-pc-linux-gnu)

Obs.: I changed the validateApiBuilds function to use a regex validation for strings into API_BUILDS variable. But I really wanted to know the reason for this behavior.

edit 2: The make-proto.config file

# define subfolder apis to build
APIS_BUILD=(
    prototests/v1
    cobrancas/v1
)
DST_DIR="."       # define the directory to store the build-in protofiles
SRC_DIR="./proto" # define the proto files folder

Please minimize your script to be a minimal reproducible example, the shortest possible thing that can be run without changes to check whether a specific problem is present -- we don't need the code checking which variables exist, f/e, unless the bug is specifically with those checks. We don't need code that prints colorful errors unless your problem is with color; etc. — Charles Duffy
– Charles Duffy, Commented Nov 20, 2020 at 16:24
BTW, for filename in $(find $SRC_DIR -name '*.proto'); do is an antipattern -- see BashPitfalls #1 describing why, and Using Find describing what to do instead. — Charles Duffy
– Charles Duffy, Commented Nov 20, 2020 at 16:26
@CharlesDuffy the behavior only occurs with all code above, if I put only the function and the "for" loop, the behavior not occurs — Bruno Luiz K.
– Bruno Luiz K., Commented Nov 20, 2020 at 16:26
Surely not. I find it impossible to believe that it would stop happening if you took out the if [[ -z "$APIS_BUILD" ]]; then block, for example. So take out as many things as you can, while leaving in only the things you can't. If that means commenting out one line or block at a time, testing, and reverting if the problem no longer occurs, do that -- see also the "Tricks for Trimming" section of sscce.org for guidance on how to build clear, minimal reproducers. — Charles Duffy
– Charles Duffy, Commented Nov 20, 2020 at 16:27
(Also, note that echo $filename is itself potentially buggy -- that's BashPitfalls #14, or the Stack Overflow question I just assigned a variable, but echo $variable prints something else!, or the shellcheck.net warning SC2086 -- running your code through shellcheck.net before asking questions here is a good idea in general). — Charles Duffy
– Charles Duffy, Commented Nov 20, 2020 at 16:31

2 revs · Accepted Answer · 2020-11-20 16:54:24Z

1

Use `find` better

for filename in $(anything) is always an antipattern -- it splits values on characters in IFS, and then expands each result as a glob. To make find emit completely unambiguous strings, use -print0:

while IFS= read -r -d '' filename; do
    [ -e "$filename" ] || continue
    echo "$filename"
done < <(find "$SRC_DIR" -name '*.proto' -print0)

Don't change IFS unnecessarily

Change your code to make the assignment to IFS be on the same line as the read, which will make IFS only be modified for that one command.

That is to say, instead of:

IFS=/
read -a SUBSTR <<<"$t"

...you should write:

IFS=/ read -a SUBSTR <<<"$t"

edited Nov 20, 2020 at 16:54

community wiki

2 revs
Charles Duffy

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1 Comment

Bruno Luiz K. Over a year ago

Works like a charm, thanks for IFS explain and the pattern for the loop

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Strange behavior using read for validate string (bash script)

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Use `find` better

Don't change IFS unnecessarily

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