Exit of Linux command-exit current Shell "return value status"

Original link: http://codingstandards.iteye.com/blog/836625 (reproduced please specify the source)

Description of Use

The exit command exits the current shell and can terminate the current script execution in a shell script.

Common parameters

Format: Exit n

Exit. Set the exit code to N. (cause the Shell to exit with a status of N.)

Format: Exit

Exit. The exit code is unchanged, which is the exit code for the last command. (If n is omitted, the exit status is the last command executed. ）

Format: $?

The exit code for the previous command.

Format: Trap "Commands" EXIT

Executes the command specified by commands when exiting. (A trap on EXIT is executed before the shell terminates.)

Exit code (Exit status, or exit code) Convention:

0 indicates success (zero-success)

Non 0 indicates failure (non-zero-failure)

2 indicates improper usage (incorrect usage)

127 indicates that the command was not found. (Command not Found)

126 means not executable (not an executable)

>=128 Signal Generation

Man 3 exit wrote the C standard specifies-constants, exit_success and Exit_failure, that May is passed to exit () to Indica Te successful or unsuccessful termination, respectively.

The following excerpt from/usr/include/stdlib.h

C code

1. #define EXIT_FAILURE 1/* failing EXIT status. */
2. #define EXIT_SUCCESS 0/* Successful EXIT status. */

#define Exit_failure    1/       * failing EXIT status.  */#define EXIT_SUCCESS    0/       * Successful EXIT status.  */

BSD tries to standardize the exit code.

Man 3 exit wrote BSD have attempted to standardize exit codes; See the file <sysexits.h>.

The following excerpt from/usr/include/sysexits.h

C code

2. #define EX_OK 0/* Successful termination */
6. #define EX__BASE */* BASE value for error messages */
10. #define EX_USAGE/* Command line USAGE error */
12. #define EX_DATAERR/* Data format Error */
14. #define EX_NOINPUT */Cannot open input */
16. #define EX_NOUSER */Addressee Unknown */
18. #define EX_NOHOST */* Host name unknown */
20. #define EX_UNAVAILABLE/* Service Unavailable */
22. #define EX_SOFTWARE */Internal software error */
24. #define EX_OSERR/* system error (e.g., can ' t fork) */
26. #define EX_OSFILE */critical OS file missing */
28. #define EX_CANTCREAT./* can ' t create (user) output file */
30. #define EX_IOERR */input/output Error */
32. #define EX_TEMPFAIL */temp failure; User is invited to retry */
34. #define EX_PROTOCOL/* Remote error in PROTOCOL */
36. #define EX_NOPERM */Permission denied */
38. #define EX_CONFIG/* Configuration Error */
42. #define EX__MAX/* Maximum listed value */

#define EX_OK 0 */Successful termination */#define EX__BASE */BASE value for error MESSAG ES */#define EX_USAGE/* Command line USAGE error */#define EX_DATAERR/* Data format Error */ #define EX_NOINPUT/Cannot open input */#define EX_NOUSER/* Addressee unknown */#define Ex_n     Ohost/* Host name unknown */#define EX_UNAVAILABLE/* Service Unavailable */#define Ex_software */* Internal software error */#define EX_OSERR//system error (e.g., can ' t fork) */#define EX_OSF ILE */Critical OS file missing */#define EX_CANTCREAT//Can ' t create (user) output file */#defi NE ex_ioerr/* input/output error */#define EX_TEMPFAIL//Temp failure; User is invited to retry */#define EX_PROTOCOL/* Remote error in PROTOCOL */#define EX_NOPERM 77/       * Permission denied * * #define Ex_config/* Configuration Error */#define EX__MAX//maximum listed value */ 

Use example one to exit the current shell

[Email protected] ~]# [[email protected] ~]# exit logout

Example two in the script, go to the directory where the script is located, or exit the bash code

1. CD $ (dirname $0) | | Exit 1

CD $ (dirname $) | | Exit 1

Example three in the script, determine the number of parameters, do not match the way you print, Exit Bash code

1. If [ "$#"-ne "2"]; Then
2. echo "Usage: $ <area>
3. Exit 2
4. Fi

If ["$#"-ne "2"]; Then    echo "Usage: $ <area> 
Example four in the script, delete temporary files when you exit bash code
 
 

  
  
 
   
Trap "Rm-f tmpfile; echo Bye. " EXIT
 
  
 
 
Trap "Rm-f tmpfile; echo Bye. " EXIT
Example five check the exit code of the previous Command bash code
 
 

  
  
 
   
./mycommand.sh
 
   
Excode=$?
 
   
If [ "$EXCODE" = = "0"];  Then
 
   
echo "O.K"
 
   
Fi
 
  
 
 
./mycommand.shexcode=$?if ["$EXCODE" = = "0"]; Then    echo "O.k" fi
Problem thinking related information
"1" 91linux Linux Exit command "2" winding streets [concept]exit n "3" Linux University Bash Shell exit Status Tutorial with practical Examples
 Exit of the Linux command-exits the current shell return value status