Login or Register to Ask a Question and Join Our Community


Shell Programming and Scripting

How to redirect stderr for <file if file does not exist?

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting How to redirect stderr for <file if file does not exist?
# 1  
Old 08-07-2014
How to redirect stderr for <file if file does not exist?
Code:
$ a=$(<missing)
-bash: missing: No such file or directory

$ a=$(<missing) 2> /dev/null
-bash: missing: No such file or directory

$ a=$(<missing 2> /dev/null)
-bash: missing: No such file or directory

$ a=$( { <missing 2> /dev/null; } )
-bash: missing: No such file or directory

$ a=$( (<missing 2> /dev/null) )
-bash: missing: No such file or directory

Here is the context (what I am trying to do):

I have some .csv files. I need to find some files that go with them to parse them in another directory but I don't know the exact directory (I do know that it contains the same number and is unique).

Code:
Parent_Folder/Excel Files_00001/File_1.csv
Parent_Folder/Excel Files_00001/File_2.csv
Parent_Folder/Excel Files_00001/File_3.csv
Parent_Folder/Run00001 - Unknown String1/DVars.xml
Parent_Folder/Run00001 - Unknown String1/valid.xml
Parent_Folder/Excel Files_00002/File_1.csv
Parent_Folder/Excel Files_00002/File_2.csv
Parent_Folder/Excel Files_00002/File_3.csv
Parent_FolderRun00002 - Unknown String2/DVars.xml
Parent_FolderRun00002 - Unknown String2/valid.xml

"DVars.xml" should always be there. It contains several parameters (including the Unknown Strings)
"valid" is usually not there and I don't want to see an error message if it is not.
Code:
            runNumber="${parentFolder:(-5)}" # Last 5 characters of Excel Files_xxxxx folder name is run number
            runFolder="$parentFolder""/../Run""$runNumber""*/" # traverse up one directory
            valFile="$runFolder""valid"
            xmlFile="$runFolder""DVars.xml"
            oIFS="$IFS"; IFS=''; # we need to expand the '*' but not split on whitespace
            [ DVarsXml="$(<$xmlFile)" ] || DVarsXml='<P2 K="RunComment" V="XML File Missing" />'
            [ valid="$(<$valFile)" 2>/dev/null ] || valid="V"
            IFS="$oIFS"

How can I prevent the stderr?

Mike
# 2  
Old 08-07-2014
Might be simplest to just not read the file, if it's not there.
Code:
[ -f "file" ] && var=$(<"file") || var=""

# 3  
Old 08-07-2014
Quote:
Originally Posted by Corona688
Might be simplest to just not read the file, if it's not there.
Code:
[ -f "file" ] && var=$(<"file") || var=""

Thanks. Actually the answer is close. var=$(<"$file") seems to block the expansion of the * while var="$(<$file)" like I had it works.

Mike
# 4  
Old 08-07-2014
Perhaps this (-r readable -s size above zero) :

Code:
[ -r $valFile -a -s $valFile ] && valid="$(<$valFile)" || valid="V"

Last edited by Chubler_XL; 08-07-2014 at 08:05 PM.. Reason: Quotes adjusted for IFS changes and wildcard expansion required in OP
# 5  
Old 08-07-2014
Quote:
Originally Posted by Michael Stora
Thanks. Actually the answer is close. var=$(<"$file") seems to block the expansion of the *
If the * expands to more than one file, that may cause problems.
# 6  
Old 08-07-2014
Another thought (fetches data from 1st file, you can do anything you like in the loop with each file expanded from *).

No need to change IFS as for "knows" about the expansion

Code:
runFolder="$parentFolder""/../Run""$runNumber""*/" # traverse up one directory
valFile="$runFolder""valid"
for x in $valFile
do
   [ -f "$x" ] && valid=$(<"$x") || valid="V"
   break
done

# 7  
Old 08-07-2014
Quote:
Originally Posted by Corona688
If the * expands to more than one file, that may cause problems.
Yes, but I know the folder numbers are unique. I another script I test the exit status of ls when there are multiple matches but in this script calling the non-builtin 'ls' bogs things down as there are about 10,000 of these files to parse.

Quote:
Originally Posted by Chubler_XL
Another thought (fetches data from 1st file, you can do anything you like in the loop with each file expanded from *).

No need to change IFS as for "knows" about the expansion

Code:
runFolder="$parentFolder""/../Run""$runNumber""*/" # traverse up one directory
valFile="$runFolder""valid"
for x in $valFile
do
   [ -f "$x" ] && valid=$(<"$x") || valid="V"
   break
done

There should only be one. If there is more than one match, I would not want to use the data. The additonal loop would slow things down. There is one predictable program writing these files so I know there is one of each type of folder for each run number.

Mike
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Redirect STDOUT & STDERR to file and then on screen

Dear all, redirecting STDOUT & STDERR to file is quite simple, I'm currently using: Code: exec 1>>/tmp/tmp.log; exec 2>>/tmp/tmp.log But during script execution I would like the output come back again to screen, how to do that? Thanks Luc edit by bakunin: please use CODE-tags like the... (6 Replies)
Discussion started by: tmonk1
6 Replies

2. Shell Programming and Scripting

Redirect STDOUT & STDERR to file and then on screen

Dear all, redirecting STDOUT & STDERR to file is quite simple, I'm currently using: exec 1>>/tmp/tmp.log; exec 2>>/tmp/tmp.logBut during script execution I would like the output come back again to screen, how to do that? Thanks Lucas (4 Replies)
Discussion started by: Lord Spectre
4 Replies

3. Shell Programming and Scripting

ksh- redirect stderr to file and then modify the file

I have the following: remsh $host -n 2>>syslog_issue_list.txt grep -i -e "EMS" -e "error" -e "warning" -e "excessive" /var/adm/syslog/syslog.log | awk /"$DATE1"/ | awk -vhost="$host" '!/remsh|telnetd/{print host "\n", $0 >> "syslog_issue_list.txt"}' I am creating a health script that has... (4 Replies)
Discussion started by: chipblah84
4 Replies

4. Shell Programming and Scripting

How to redirect stderr to a file as well

Hello everyone, I'm a nooby in Linux, and I need some help. I have a shell script like this: echo "Start of script" > ../My_Log_Dir/Script_Name.log .. cp ../My_DataIn/File.txt ../My_DataOut/ 2>> ../My_Log_Dir/Script_Name.log rc=$? .. echo "End of Script" >>... (5 Replies)
Discussion started by: H.Faria
5 Replies

5. Shell Programming and Scripting

redirect stdout and stderr to file wrong order problem with subshell

Hello I read a lot of post related to this topic, but nothing helped me. :mad: I'm running a ksh script with subshell what processing some ldap command. I need to check output for possible errors. #!/bin/ksh ... readinput < $QCHAT_INPUT |& while read -p line do echo $line ... (3 Replies)
Discussion started by: Osim
3 Replies

6. Shell Programming and Scripting

Redirect stdout/stderr to a file globally

Hi I am not if this is possible: is it possible in bach (or another shell) to redirect GLOBALLY the stdout/stderr channels to a file. So, if I have a script script.sh cmd1 cmd2 cmd3 I want all stdout/stderr goes to a file. I know I can do: ./script.sh 1>file 2>&1 OR ... (2 Replies)
Discussion started by: islegmar
2 Replies

7. UNIX for Dummies Questions & Answers

Redirect just stderr to a file with a timestamp

I'm using below command to redirect stderr to a file but I also want to add timestamp to stderr.out to find out the date / time the error occurred. ls -ltr 2>>/tmp/stderr.out Thanks (5 Replies)
Discussion started by: mbak
5 Replies

8. Shell Programming and Scripting

How to redirect stderr and stdout to a file

Hi friends I am facing one problem while redirecting the out of the stderr and stdout to a file let example my problem with a simple example I have a file (say test.sh)in which i run 2 command in the background ps -ef & ls & and now i am run this file and redirect the output to a file... (8 Replies)
Discussion started by: sushantnirwan
8 Replies

9. Shell Programming and Scripting

how can i redirect stderr to file in Make?

Hello all im using tcsh shell on sun Solaris , using the Make utility for compilation i will like to be able to redirect the stderr to file , how can it be done ? (0 Replies)
Discussion started by: umen
0 Replies

10. Shell Programming and Scripting

Redirect stdout and stderr

How can I redirect and append stdout and stderr to a file when using cron? Here is my crontab file: */5 * * * * /dir/php /dir/process_fns.php >>& /dir/dump.txt Cron gives me an 'unexpected character found in line' when trying to add my crontab file. Regards, Zach Curtis POPULUS (8 Replies)
Discussion started by: zcurtis
8 Replies
Login or Register to Ask a Question