grep behaving differently in bash script than in interactive shell [duplicate]

Question

In my bash script, I am attempting to parse through a status file and detect errors based on some keywords. I store these prefixes in a list, and then loop through them.

Bash script:

status_page="/path/to/file.txt"
list="aaa bbb ccc ddd"

for pre in $list
do
    echo "grep '\w\w\w${pre}-.*\.lin failed' ${status_page}" # debug
    if grep '\w\w\w${pre}-.*\.lin failed' ${status_page}; then
        echo "Found error!"
        exit 8;
    fi
done

/path/to/file.txt:

xyzfff-tool.lin failed
xyzggg-exec.lin failed
rstccc-tool.lin failed

The bash script should catch the line rstccc-tool.lin failed, but it skips right over it.

For debugging, I print the grep commands verbatim, and when I copy that line and issue the command in my shell (tcsh), it returns that line...

Shell:

$ grep '\w\w\wccc-.*\.lin failed' /path/to/file.txt
    rstccc-tool.lin failed
$ echo $?
0

If grep can find the line when I issue the command normally, how come it won't find it when the bash script is calling grep?

user000001 · Accepted Answer · 2013-09-05 17:32:03Z

6

The variable won't be expanded in single quotes. Try with double quotes:

if grep "\w\w\w${pre}-.*\.lin failed" "${status_page}"; then

answered Sep 5, 2013 at 17:32

user000001

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1 Comment

tomocafe Over a year ago

Sure enough... that solved it all. Thanks for the quick solution. :) Will accept the answer in... 9 minutes.

macetw · Accepted Answer · 2013-09-05 17:40:12Z

2

The ${pre} portion of that script is not parsing it correctly. I believe you need that line to say:

if grep '\w\w\w'${pre}'-.*\.lin failed' ${status_page}; then

... where the ${pre} is outside the quotation, such that bash will do the correct string replacement before sending it to grep.

answered Sep 5, 2013 at 17:40

macetw

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