How to debug shell scripts
1) Check for syntax errors: Generally speaking, we can modify the source code of shell scripts to make them output relevant debugging information to locate errors, so is there a way to debug shell scripts without modifying the source code? The answer is to use the shell’s execution options, the following are some common options: -n only reads the shell script, but does not actually execute it -x to enter the trace mode, displaying every command executed -c “string” reads commands from strings “-n” can be used to test the shell script for syntax errors. It can be used to test shell scripts for syntax errors, but does not actually execute the commands. It is a good practice to use the “-n” option to test shell scripts for syntax errors after they have been written and before they are actually executed. This is because some shell scripts have an effect on the system environment when they are executed, such as generating or moving files, and if you find a syntax error when you are actually executing the script, you will have to manually do some restoration of the system environment before you can continue to test the script. The “-c” option causes the shell interpreter to read and execute shell commands from a string rather than from a file. This option can be used when you need to temporarily test the execution of a small piece of script as follows: sh-c’a=1;b=2;letc=$a+$b;echo “c=$c”‘ The “-x” option can be used to trace the execution of a script and is a powerful tool for debugging shell scripts. The “-x” option causes the shell to display every command line it actually executes as it executes the script, and to display a “+” sign at the beginning of the line.” The + sign is followed by the contents of the command line after variable substitution, which helps to analyze what command was actually executed. The “-x” option is simple and easy to use, and can easily deal with most shell debugging tasks, and should be taken as the preferred means of debugging. 2) Debugging Tools – bashdb Use the shell debugger bashdb, which is a debugging tool similar to the GDB, to complete the shell script to set breakpoints, single-step execution, and so on. This is a debugging tool similar to GDB, which can accomplish many functions such as setting breakpoints on shell scripts, single-step execution, and variable observation. Common commands for debugging with bashdb 1. List code and query code classes: l lists the 10 lines below the current line – lists the first 10 lines of the line of code being executed. w lists the 10 lines before the line of code being executed. w lists the 10 lines before the line of code being executed. Go back to the line of code being executed w List the code before and after the line of code being executed /pat/ Search backward for pat?pat?search forward for pat2.Debug Control Classes: h Helphelp command to get command-specific information q Exit bashdbx Arithmetic Expressions Calculate the value of the arithmetic expression and display it!!!! Space Shell Command Arguments Execute shell commands Common commands for debugging with bashdb (cont.) Control Script Execution Classes: n Execute the next statement, encounter the function, do not enter the function inside the execution, treat the function as a black box sn Execute the function n times in a single step, encounter the function and enter the function inside the function b Line number n Set a breakpoint at line number n del Line number n Undo the breakpoint at line number n the breakpoint at line n
Can C be used in shell scripts
C can be used to execute external shell scripts through system() calls, but C code cannot be executed directly in shell scripts.
Because shell scripts are interpreted, C code can only be recognized by the C compiler, and needs to be compiled into an executable file before it can be called in a shell script.
The environment in the awk text processing tool is basically C syntax, so if awk is used in a shell script, it is possible to use C syntax directly.
How to call a shell script file in a c program
How to call a shell script file in a c program
int iRetCode;
char sStr[100];
sprintf(sStr, “home/test/upload/unload.sh”);
iRetCode= system(sStr);
if(iRetCode<0)
{
printf(“shell error!”);
}