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Top Forums Shell Programming and Scripting String concatenation not working in a loop Post 302389811 by LostInTheWoods on Tuesday 26th of January 2010 02:34:56 AM
Old 01-26-2010
String concatenation not working in a loop

Hi,

First post, so I hope someone can help me with this weirdness Smilie

I have a number files with some rows of information I want to extract, at the same time I want to add to a string some details from the file. I have found two different ways of looping over rows in a file, but one method doesn't let me concatenarte strings and I don't know why....

The first method sets the IFS environmental variable. I don't really favour this method, but it works..

Code:
#!/bin/bash -
OLDIFS=$IFS
IFS='
'

STE="cat"
  
for FILE in $( ls *-df | cut -f 4 -d / ); do
  N=0
  for LINE in $( cat $FILE ); do
    N=$((N+1))
    STE="$STE""dog"
  done
done
echo "$STE" && exit

and produces:
catdogdogdogdogdogdogdogdogdogdogdogdogdogdogdogdo gdogdogdogdogdogdogdogdogdogdogdogdog


Method 2 uses "read" but prevents the concatenation of the string:
Code:
#!/bin/bash -
STE="cat"
  
for FILE in $( ls *-df | cut -f 4 -d / ); do
  N=0
  cat "$FILE" | while read LINE ; do
    N=$((N+1))
    STE="$STE""dog"
  done
done
echo "$STE" && exit

and produces:
cat

Why is there a difference in the two methods? I would rather not be changing environmental variables and a simple loop is my preferred choice.

Thanks for your help, as this has been driving me crazy...
Stephen
 

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RBASH(1)						      General Commands Manual							  RBASH(1)

NAME
rbash - restricted bash, see bash(1) RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow- ing are disallowed or not performed: o changing directories with cd o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV o specifying command names containing / o specifying a file name containing a / as an argument to the . builtin command o specifying a filename containing a slash as an argument to the -p option to the hash builtin command o importing function definitions from the shell environment at startup o parsing the value of SHELLOPTS from the shell environment at startup o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators o using the exec builtin command to replace the shell with another command o adding or deleting builtin commands with the -f and -d options to the enable builtin command o using the enable builtin command to enable disabled shell builtins o specifying the -p option to the command builtin command o turning off restricted mode with set +r or set +o restricted. These restrictions are enforced after any startup files are read. When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. SEE ALSO
bash(1) GNU Bash-4.0 2004 Apr 20 RBASH(1)
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