I get "syntax error near unexpected token `done' " when I use while loop in bash

Question

I have a file which filled in streaming way line by line. I need to decrease the volume of the file by deleting the oldest record in it. I would like to count the number of lines and if the number of lines exceed than 100 then delete the oldest lines. However I got the following error:

./1.sh: line 18: syntax error near unexpected token `done'
./1.sh: line 18: `done'

Here is my code:

#!/bin/bash
FILE="11.txt"
linenum=0

while true; do

#Count number of lines
linenum=`cat "$FILE" | wc -l`

while [ $linenum -gt 100 ] do

#Delete the head of file (oldest)
sed -i 1,1d "$FILE"

#Count number of lines
linenum=`cat "$FILE" | wc -l`

done

done

Can you please help me?

This isn't safe. sed -i (effectively) makes a copy of the input file, then replaces the original with the modified copy. If the original is written to while sed is working on the copy, those changes are lost. — chepner
– chepner, Commented May 18, 2017 at 13:24
Whatever is writing to the file needs to be responsible for trimming it. — chepner
– chepner, Commented May 18, 2017 at 13:46
@chepner: It does't work! when I applied it on a streaming file, it could't work! :(( — user7581013
– user7581013, Commented May 18, 2017 at 15:10

Aaron · Accepted Answer · 2017-05-18 12:43:41Z

4

You need a linefeed or a ; between the while's condition and the do :

while [ $linenum -gt 100 ]; do

    #Delete the head of file (oldest)
    sed -i 1,1d "$FILE"

    #Count number of lines
    linenum=$(wc -l "$FILE")

done

I also indented the code properly, changed the subshell `...` notation to the more modern $(...) and removed a redundant use of cat.

edited May 18, 2017 at 12:43

answered May 18, 2017 at 12:38

Aaron

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Comments

Krishnom · Accepted Answer · 2017-05-18 12:44:03Z

0

You missed the semicolon at below line

while [ $linenum -gt 100 ] do

should be

while [ $linenum -gt 100 ] ; do

Hope this helps.

answered May 18, 2017 at 12:44

Krishnom

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