Example: Saving and restoring system-level environment variables
These ILE C programs show how to save the current set of system-level environment variables and restore them later.
Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.
Saving system-level environment variables
This program saves the system-level environment variables and the associated CCSIDs in a file for restoring later.
Use the Create C Module (CRTCMOD) and the Create Program (CRTPGM) commands to create this program.
Call this program with one parameter (the file to store the variable list and the CCSIDs).
/******************************************************************/
/******************************************************************/
/* */
/* FUNCTION: Save the system-level environment variable list */
/* and the CCSIDs in a file */
/* */
/* LANGUAGE: ILE C */
/* */
/* APIs USED: Qp0zGetAllSysEnv() */
/* */
/******************************************************************/
/******************************************************************/
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#include <qp0z1170.h>
int main(int argc, char *argv[])
{
int fd, bw, rc;
int listBufSize, ccsidBufSize, *ccsidBuf;
char *listBuf;
int numvar, sl, sc;
if(argc != 2)
{
printf("Usage: call %s <filename>\n",argv[0]);
printf("Example: call %s '/tmp/sev'\n",argv[0]);
return -1;
}
sl = listBufSize = 1000;
sc = ccsidBufSize = 1000;
listBuf = (char *)malloc(listBufSize);
ccsidBuf = (int *)malloc(ccsidBufSize);
/* Create a file of specified name */
/* If it exists, it is cleared out */
/* Opened for writing */
fd = open(argv[1], O_CREAT | O_WRONLY | O_TRUNC, S_IRWXU);
if(fd == -1)
{
printf("open() failed. errno = %d\n", errno);
return -1;
}
rc = Qp0zGetAllSysEnv(listBuf, &listBufSize, ccsidBuf,
&ccsidBufSize, NULL);
if(rc != 0)
{
/* If there are no variables to save, write a */
/* zero into the file and return success */
if(rc == ENOENT)
{
numvar = 0;
bw = write(fd, &numvar, sizeof(int));
close(fd);
printf("No system-level environment variables to save");
return 0;
}
if(rc != ENOSPC)
{
printf("Error using Qp0zGetAllSysEnv(), errno = %d\n", rc);
return -1;
}
/* rc = ENOSPC. size of buffer is not enough */
/* change buffer size and try again */
/* If listBuf is not large enough, */
/* allocate more space */
if(listBufSize > sl)
{
listBuf = (char *)realloc(listBuf, listBufSize);
}
/* If ccsidBuf is too small, allocate */
/* more space */
if(ccsidBufSize > sc)
{
ccsidBuf = (int *)realloc(ccsidBuf, ccsidBufSize);
}
rc = Qp0zGetAllSysEnv(listBuf, &listBufSize,
ccsidBuf, &ccsidBufSize, NULL);
if(rc != 0)
{
printf("Error using Qp0zGetAllSysEnv(), errno = %d\n", rc);
return -1;
}
}
/* Write the contents of the buffer into the file */
/* First write the total number of ccsid values */
/* This is the total number of variables */
numvar = ccsidBufSize/sizeof(int);
bw = write(fd, &numvar, sizeof(int));
if(bw == -1)
{
printf("write() of total number of ccsids failed. errno = %d\n", errno);
return -1;
}
/* Next write the ccsid values */
bw = write(fd, ccsidBuf, ccsidBufSize);
if(bw == -1)
{
printf("write() of ccsid values failed. errno = %d\n", errno);
return -1;
}
/* Now write the size (in bytes) of the listBuf */
bw = write(fd, &listBufSize, sizeof(int));
if(bw == -1)
{
printf("write() of listBufSize failed. errno = %d\n", errno);
return -1;
}
/* Finally write the listBuf containing the variable strings*/
bw = write(fd, listBuf, listBufSize);
if(bw == -1)
{
printf("write() of listBuf failed. errno = %d\n", errno);
return -1;
}
/* Close the file */
rc = close(fd);
if(rc != 0)
{
printf("close() failed. errno = %d\n", errno);
return -1;
}
printf("System-level environment variables saved\n");
return 0;
}Restoring system-level environment variables
This program reads the system-level environment variable list from a file and then sets the system-level environment variables.
Use the Create C Module (CRTCMOD) and the Create Program (CRTPGM) commands to create this program.
Call this program with one parameter (the name of the file in which the system-level environment variables were stored).
/******************************************************************/
/******************************************************************/
/* */
/* FUNCTION: Restore the system-level environment variable list */
/* and the associated CCSIDs stored in a file */
/* */
/* LANGUAGE: ILE C */
/* */
/* APIs USED: Qp0zPutSysEnv() */
/* */
/******************************************************************/
/******************************************************************/
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#include <qp0z1170.h>
int main(int argc, char *argv[])
{
int fd, rc, br, i, numvar;
int ccsidBufSize = 0, listBufSize = 0, *ccsidBuf;
char *listBuf;
if (argc != 2)
{
printf("Usage: call %s <filename>\n",argv[0]);
printf("Example: call %s '/tmp/sev'\n",argv[0]);
return -1;
}
/* Open the file specified */
fd = open(argv[1], O_RDONLY);
if(fd == -1)
{
printf("open() failed. errno = %d\n", errno);
return -1;
}
/* Get the number of variables */
br = read(fd, &numvar, sizeof(int));
if(br == -1)
{
printf("read() failed. errno = %d\n", errno);
return -1;
}
/* Could delete the existing system-level environment */
/* variables and have only the restored values. */
/* If so desired, could call Qp0zDltSysEnv() to do so */
/* If there aren't any elements in the file, skip the rest of */
/* the reads and go to the end */
if(numvar > 0)
{
ccsidBufSize = numvar*sizeof(int);
ccsidBuf = (int *)malloc(ccsidBufSize);
/* Read the ccsid values and put it in ccsidBuf */
br = read(fd, ccsidBuf, ccsidBufSize);
if(br == -1)
{
printf("read() failed. errno = %d\n", errno);
return -1;
}
/* Read the size of the list buffer and put it in listBufSize */
br = read(fd, &listBufSize, sizeof(int));
if(br == -1)
{
printf("read() failed. errno = %d\n", errno);
return -1;
}
listBuf = (char *)malloc(listBufSize);
/* Finally read the strings themselves */
br = read(fd, listBuf, listBufSize);
if(br == -1)
{
printf("read() failed. errno = %d\n", errno);
return -1;
}
}
/* Walk through the buffer and get the */
/* name=value strings one by one */
/* Use Qp0zPutSysEnv() to set the values */
for(i = 0; i < numvar; i++)
{
rc = Qp0zPutSysEnv(listBuf, ccsidBuf[i], NULL);
if(rc != 0)
{
printf("Qp0zPutSysEnv() failed. rc=%d\n",rc);
return -1;
}
listBuf += strlen(listBuf) + 1;
}
close(fd);
printf("System-level environment variables restored\n");
return 0;
}