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Old 01-25-2013, 02:26 PM   #1
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Bash problem

I have started a small bash script and I want to analyze a file. The file contains lines that start with the keywords [menu] or [data]. In the following script none of the keywords are recognized.

#Example lines:
[menu] non-RT ...........................

[data] CFG ............................
local DI=0
local IN=0

while read line
    line=$(echo $line | sed s/^\ *//)
    if [[ $line =~ ^\\[menu\\] ]]
      line=$(echo "$line" | sed s/\\[menu\\]\ *//)
      let IN++
    elif [[ $line =~ ^\\[data\\] ]]
      line=$(echo "$line" | sed s/\\[data\\]\ *//)
      let DI++
What have I done wrong in the if and elif statement?

Last edited by Curiosity42; 01-25-2013 at 03:15 PM. Reason: Formatting of script
Old 01-25-2013, 03:30 PM   #2
Ser Olmy
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Change the double backslashes to single backslashes. As they stand, your expressions match "\menu\" and "\data\" at the start of a line.

Edit: Actually, the current expressions match "\m" and "\d" followed by characters from the sets "enu\" and "ata\" respectively.

Last edited by Ser Olmy; 01-25-2013 at 03:38 PM.
Old 01-25-2013, 11:58 PM   #3
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To add to the above, you also do not need to escape the space.
Old 01-26-2013, 12:40 AM   #4
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I suggest using case statement instead:
while read LINE; do
    case "$LINE" in
        while read LINE; do
            : do something
        while read LINE; do
            : do something
        # invalid line?
done < "$YOURFILE"

Last edited by konsolebox; 01-26-2013 at 12:41 AM.
Old 01-27-2013, 02:37 PM   #5
David the H.
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What konsolebox said.

In addition, you usually don't need sed for this kind of thing, when you have lots of powerful string manipulation features already built into the shell.

To remove all whitespace at the start of the variable string, for example:

shopt -s extglob
And when using the shell's built-in regex ability, store the expression in a variable first (using hard quotes), then use that inside the [[..]] brackets, unquoted. This will make it easier to compose them without having to fiddle with all the backslashes.

if [[ $line =~ $re ]]; then
And please use ***[code][/code]*** tags around your code and data, to preserve the original formatting and to improve readability. Do not use quote tags, bolding, colors, "start/end" lines, or other creative techniques.

Last edited by David the H.; 01-27-2013 at 02:42 PM. Reason: added another point


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