| C/TC shell scripts often fail because of some simple syntax error or logic error. Options to the csh command to help you debug your programs are provided in Table 10.3. Example 10.7. (The -v and -x Options) 1 % cat practice #!/bin/csh echo Hello $LOGNAME echo The date is `date` echo Your home shell is $SHELL echo Good-bye $LOGNAME 2 % csh -v practice echo Hello $LOGNAME Hello ellie echo The date is `date` The date is Sun May 23 12:24:07 PDT 2004 echo Your login shell is $SHELL Your login shell is /bin/csh echo Good-bye $LOGNAME Good-bye ellie 3 % csh -x practice echo Hello ellie Hello ellie echo The date is `date` date The date is Sun May 23 12:24:15 PDT 2004 echo Your login shell is /bin/csh Your login shell is /bin/csh echo Good-bye ellie Good-bye ellie Table 10.3. echo (“x) and verbose (“v) | Option | What It Does | | As Options to csh and tcsh | | csh x scriptname tcsh -x scriptname | Display each line of script after variable substitution and before execution. | | csh v scriptname tcsh -v scriptname | Display each line of script before execution, just as you typed it. | | csh n scriptname tcsh -n scriptname | Interpret but do not execute commands. | | As Arguments to the set Command | | set echo | Display each line of script after variable substitution and before execution. | | set verbose | Display each line of script before execution, just as you typed it. | | As the First Line in a Script | | #!/bin/csh xv #!/bin/tcsh -xv | Turns on both echo and verbose. These options can be invoked separately or combined with other csh invocation arguments. | EXPLANATION -
The contents of the C shell script are displayed. Variable and command substitution lines are included so that you can see how echo and verbose differ . -
The “v option to the csh command causes the verbose feature to be enabled. Each line of the script is displayed as it was typed in the script, and then the line is executed. -
The “x option to the csh command enables echoing. Each line of the script is displayed after variable and command substitution are performed, and then the line is executed. Because this feature lets you examine what is being replaced as a result of command and variable substitution, it is used more often than the verbose option. Example 10.8. (Echo and Verbose) 1 % cat practice #!/bin/csh echo Hello $LOGNAME echo The date is `date` set echo echo Your home shell is $SHELL unset echo echo Good-bye $LOGNAME % chmod +x practice 2 % practice Hello ellie The date is Sun May 26 12:25:16 PDT 2004 --> echo Your login shell is /bin/csh --> Your login shell is /bin/csh --> unset echo Good-bye ellie EXPLANATION -
The echo option is set and unset within the script. This enables you to debug certain sections of your script where you have run into a bottleneck, rather than echoing each line of the entire script. -
The “ “> marks where the echoing was turned on. Each line is printed after variable and command substitution and then executed. Example 10.9. 1 % cat practice #!/bin/csh echo Hello $LOGNAME echo The date is `date` set verbose echo Your home shell is $SHELL unset verbose echo Good-bye $LOGNAME 2 % practice Hello ellie The date is Sun May 23 12:30:09 PDT 2004 --> echo Your login shell is $SHELL --> Your login shell is /bin/csh --> unset verbose Good-bye ellie EXPLANATION -
The verbose option is set and unset within the script. -
The “ “> marks where verbose was turned on. The lines are printed just as they were typed in the script and then executed. |