IF -a condition meaning.


 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers IF -a condition meaning.
# 1  
Old 10-30-2013
IF -a condition meaning.

Hi All,

Could you please let me know what is the meaning of below -a condition if the if?

Code:
if ! [ -a $SOURCEPATH/$SOURCEFILE_A ]

Thanks in advance for the help.

Last edited by Scrutinizer; 10-30-2013 at 01:14 PM.. Reason: code tags added
# 2  
Old 10-30-2013
# 3  
Old 10-30-2013
Thanks a lot Yoda for the help. Smilie
And what is the difference between -a and -f.
It says -f is for regular file and -a is it for any file. Am i correct.?
# 4  
Old 10-30-2013
Quote:
Originally Posted by abhi_123
Thanks a lot Yoda for the help. Smilie
And what is the difference between -a and -f.
It says -f is for regular file and -a is it for any file. Am i correct.?
That is correct.

E.g. you can verify this by creating a named pipe (FIFO) using mkfifo:
Code:
$ mkfifo file.pipe
$ [ -a file.pipe ] && echo "True" || echo "False"
True
$ [ -f file.pipe ] && echo "True" || echo "False"
False

# 5  
Old 10-30-2013
Note: -a may happen to be supported for historical reasons, however, it is not part of POSIX so -e should be used instead.

Quote:
An early proposal used the KornShell -a primary (with the same meaning), but this was changed to -e because there were concerns about the high probability of humans confusing the -a primary with the -a binary operator.
test: Rationale
This User Gave Thanks to Scrutinizer For This Post:
 
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Meaning of $1^

Hello everyone, I'm looking for the meaning of this expression, as I don't understand it quite clearly : $1^ What do you think it could be? I thought either: - match lines starting with argument 1 but it should be ^$1 - turn line around : word becomes drow Thanks in advance for your... (4 Replies)
Discussion started by: bibelo
4 Replies

2. Shell Programming and Scripting

If condition return 0 even when it fails to satisfy te condition

HI My doubt may be basic one but I need to get it clarified.. When i use "if" condition that checks for many AND, OR logical conditions like if ]; then return 0 fi Even the if condition fails it returns as zero.. Any clue.. But if i add else condition like if ]; ... (2 Replies)
Discussion started by: Priya Amaresh
2 Replies

3. Shell Programming and Scripting

redirect stdout echo command in condition A run in condition B

hi, I have some problems in my simple script about the redirect echo stdout command inside a condition. Why is the echo command inside the elif still execute in the else command Here are my simple script After check on the two diff output the echo stdout redirect is present in two diff... (3 Replies)
Discussion started by: jao_madn
3 Replies

4. UNIX for Dummies Questions & Answers

meaning of <<!

Hi all, I wanna know the meaning of the last word "<<! " sudo su - user <<! please help on this !!!! (1 Reply)
Discussion started by: sudharson
1 Replies

5. HP-UX

Difference between [condition] and [[condition]] and ((condition)) when used with if condition

Executed the following if conditions .. and got different results . only (( )) gave correct o/p with all scenarios . Can anybody please let me know what is the difference between and ] and ((condition)) when used with if condition. And why each condition gave different result. 1.... (2 Replies)
Discussion started by: soumyabubun
2 Replies

6. Shell Programming and Scripting

meaning of !*

can someone please tell what !* means in shell syntax. Regards, (3 Replies)
Discussion started by: busyboy
3 Replies

7. UNIX for Dummies Questions & Answers

what the meaning of #*

can some one please tell the meaning of the second statement i.e n=${m#*=} i couldnt get the meaning of the #*= 1.) m="mohit=/c/main/issue" echo $m result ----------- mohit=/c/main/issue 2.) n=${m#*=} echo $n RESULT ------- /c/main/issue (1 Reply)
Discussion started by: narang.mohit
1 Replies

8. UNIX for Dummies Questions & Answers

Use and meaning of $*

Can someone explain the use and meaning of "$*" expression. (2 Replies)
Discussion started by: sinpeak
2 Replies

9. AIX

meaning of ${0%${0##*/}}

. ${0%${0##*/}}Script_Name if i issue this command, it is executing the script. can any one tell what is the meaning of ${0%${0##*/}} (7 Replies)
Discussion started by: nyelavarthy
7 Replies

10. Shell Programming and Scripting

what is the meaning here?

#!/bin/sh $ORACLE_HOME/bin/sqlplus -S $orauserid/$orapasswd@$oradb << _TMP alter session set nls_date_format = 'YYYYMMDD HH24:MI'; set linesize 100 set pagesize 400 ok the above is part of a script..i just wanna know what does sqlplus -S means?? as in why we need to insert the -S behind? (2 Replies)
Discussion started by: forevercalz
2 Replies
Login or Register to Ask a Question