While Loop Syntax help needed


Login or Register for Dates, Times and to Reply

 
Thread Tools Search this Thread
# 1  
Error While Loop Syntax help needed

Hi everyone,

Can ny1 help me out regarding while loop arguments

i.e. what does

Code:
-gt
-ge
-lt
-le

means?

actually i am new to while loops
# 2  
You can find the answers here:

Unix shell scripting with sh/ksh

Regards
# 3  
Simple syntax:
Code:
while command_exit_code_is_zero
do
    somecmd1
    somecmd2
done

-lt, -gt, ... are options of test command, look shell builtin test (= also [ ] )

After while is some command line, shell will do it, check exit code and if it's 0 = okay, then do the command lines between do and done.

while true
while cp x y
while (( i < 100 ))
while [ "$some" -lt 100 ]
while test "$some -lt 100
while [ "$some" = "1" ]
while read line
while :
...
: is command, which is builtin and give always exit 0 status ( shell's nop command), do nothing. Today also true and false are builtin commands, so those are more "readable" as :

You can break the loop using command break.

You can jump to the while line using command continue.
ex.
Code:
while read line
do
      case "$line" in
           "") continue  ;;    # next line
           end*) break ;;     # end this while
      esac
      do_some_for "$line"
done

Login or Register for Dates, Times and to Reply

Previous Thread | Next Thread
Thread Tools Search this Thread
Search this Thread:
Advanced Search

Test Your Knowledge in Computers #484
Difficulty: Medium
A compiler transforms source code into object code, a floating point number format that machines understand.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

What does xx mean in this while loop syntax?

I have a shell script which has this while loop line "while read tblName xx; do..." I understand how while loop works but don't know what does this xx stands for? (1 Reply)
Discussion started by: later_troy
1 Replies

2. UNIX for Dummies Questions & Answers

Syntax error in for loop

I am using simple for loop, but getting syntax error when I run the code code #!/bin/ksh pls enter number read n for(i=1; i<=n; i++) do echo $i done syntax error + pls enter number + read n (5 Replies)
Discussion started by: stew
5 Replies

3. Shell Programming and Scripting

IF loop syntax error

I am trying to run a menu option though IF loops. I keep getting errors not allowed the menu to be processed correctly. Currently it will accept the first 2 statements but then crash on the 3rd. The 2nd and 3rd have the same syntax, so I do not understand why it breaks. #!/bin/bash while... (4 Replies)
Discussion started by: Ironguru
4 Replies

4. Shell Programming and Scripting

Syntax error: Bad for loop variable

I'm getting an error while running this script. Need help. set -x verbose #echo on clear #clear the screen USERNAME="bbb" PASSWORD="password" SERVER="192.168.1.100" WAIT_TIME=300 FILE_PATH="/home/users/xxx/MMM" # local directory to pickup *.dat file REMOTE_PATH="/Drop_off/xxx/yyy" #... (17 Replies)
Discussion started by: clgz2002
17 Replies

5. UNIX for Dummies Questions & Answers

for-loop syntax

%%%%% (3 Replies)
Discussion started by: lucasvs
3 Replies

6. Shell Programming and Scripting

for loop syntax

hi, I have to use for loop in my script. The below code is providing an output, 1,2,3,4,5..n. But i need to display the values one by one eg: it has to display the first value then exit from the loop and display the second value then exit till n(last value). for i in 1,2,3,4,5..n do ... (2 Replies)
Discussion started by: sreelu
2 Replies

7. Shell Programming and Scripting

Shell syntax checker available, or is a new project needed?

I'd like a shell-script syntax checker that can detect at least the following errors, and more: 1. Variable $VAR used but VAR has not been defined. 2. Variable VAR defined but never used. 3. Use of unquoted variables which might break external commands e.g. SOMETHING in: value=`grep $SOMETHING... (5 Replies)
Discussion started by: garethr
5 Replies

8. Shell Programming and Scripting

Problems with syntax in a loop (AWK)

Hi guys, I'm trying to loop through a number of files that is set by whatever is in a field. eg. The idea is to split FILELIST down into fields, it could contain 1 - 999 fields and it's bar delimited. I thought simple, count the number of fields in the field and then loop... (1 Reply)
Discussion started by: Peejay
1 Replies

9. Shell Programming and Scripting

syntax error in while loop

Hi, I have the following script (compile_mercury) and I get this error: I have no idea why...and I have written this script completely in linux (bash) and not in windows. **************** ./compile_mercury: line 136: syntax error near unexpected token `done' ./compile_mercury: line 136:... (1 Reply)
Discussion started by: habzone2007
1 Replies

10. Shell Programming and Scripting

for loop syntax trouble

i don't get what's wrong here. i'm writing a shell script that takes 1 argument (a number) from the command-line, but it's throwing an error: Syntax error: Bad for loop variable doesn't make much sense for (( i = 1; i = ${1}; i++ )) # error points to this line everytime do echo... (9 Replies)
Discussion started by: visitorQ
9 Replies

Featured Tech Videos