What is the maximum number of characters that the ksh variable accepts?

问题

I am trying to load and parse a really large text file. Although the loading is not a problem, but there are particular lines that have 2908778 characters on a single line.

This is causing an error in my script.

On the script below, I removed all logic and just got straight to read line. I also removed all valid lines and just left the really long line in one text file. When running I get the below error :

$ dowhiledebug.sh dump.txt
dowhiledebug.sh[6]: no space
Script Ended dump.txt

The actual script:

 #!/bin/sh
 filename=$1
 count=1
 if [ -f ${filename} ]; then
    echo "after then"
    while read line;
            do
            echo "$count"
            count=$((count+1))
            done < $filename
 else
    echo "Could not open file $filename"
 fi
 echo "Script Ended $filename"

Updated (2013-01-17)

Follow up question : Is it possible to increase the maximum number of characters that ksh variable accepts?

回答1:

The limit for any shell is the limit of the C command line maximum. Here's a little program that pulls the information out of /usr/include/limits.h for you:

cpp <<HERE | tail -1
#include <limits.h>
ARG_MAX
HERE

Mine gives me (256 * 1024) or 262144 characters.

Doesn't work if the C compiler isn't installed, but it's probably a similar limit.

回答2:

what OS and version of ksh? Can you echo ${.sh.version} and get a value? If so, please include in your question above. Or could this be pdksh?

Here's a test that will get you in the ballpark, assuming a modern ksh supporting (( i++ )) math evaluations:

#100 char var
var=1234578901234456789012345678901234567890123456789012345789012344567890123456789012345678901234567890

$ while (( i++ < 10000 )) ;do  var=$var$var ; print "i=$i\t" ${#var} ; done
i=1      200
i=2      400
i=3      800
i=4      1600
i=5      3200
i=6      6400
i=7      12800
i=8      25600
i=9      51200
i=10     102400
i=11     204800
i=12     409600
i=13     819200
i=14     1638400
i=15     3276800
i=16     6553600
i=17     13107200
i=18     26214400
i=19     52428800
i=20     104857600
i=21     209715200
i=22     419430400
-ksh: out of memory

$ print -- ${.sh.version}
Version JM 93t+ 2010-05-24

IHTH

来源：https://stackoverflow.com/questions/14371326/what-is-the-maximum-number-of-characters-that-the-ksh-variable-accepts

标签

bash

shell

unix

ksh