Linux C Programming File Operation jobs

The contents of the A.txt file are as follows:
32
45
65
32
67
454
89
54
24
75
3
67
890
32
1
1, write a program to read the A.txt file, the file content number from small to large sorting, and the results of the sorting to write B.txt

#include <stdio.h> #include <errno.h> #include <string.h> #include <stdlib.h>void sort (int *a,    int n) {int i, j, temp; for (j = 0, J < n-1; J + +) {for (i = 0; i < n-1-J; i++) {if (A[i] > a[i + 1])                array element size in ascending order {temp = A[i];                A[i] = a[i + 1];            A[i + 1] = temp;    }}}}int Main () {//read a.txt FILE *FPA = NULL;    FPA = fopen ("A.txt", "R");        if (FPA = = NULL) {printf ("FPA open error:%s", strerror (errno));    return-1;    } int buf[100];    memset (buf, 0, sizeof (BUF));    Char val[100];    int ilen = 0;        while (1) {memset (val, 0, sizeof (Val));        if (Fgets (Val, sizeof (Val), FPA) = = NULL) {break;        } Buf[ilen] = Atoi (val);        printf ("buf[%d]=%d\n", Ilen, Buf[ilen]);    ilen++;    } fclose (FPA);    Sorts sort (buf, ilen);    Write b.txt FILE *FPB = NULL; FPB = fopen ("B.txt", "w");        if (FPB = = NULL) {printf ("FPB open error:%s", strerror (errno));    return-1;    } int loop = 0;        for (loop = 0; loop < Ilen; loop++) {memset (val, 0, sizeof (Val));        sprintf (Val, "%d\n", Buf[loop]);    Fputs (Val, FPB);    } fclose (FPB); return 0;}

2, by reading the relevant files under the/proc, get the system CPU information, memory information.

#include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include <sys/types.h># Include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #include < stdlib.h>/* string parsing *//* Open file, the string to be found in the file, the returned data address *///char *start;char *parse_string (char *file, char *string) {static C    Har resultstr[100];    memset (resultstr, 0, sizeof (RESULTSTR));    int FD;    Char pbuf[1024*10];    int nread;    Char *ptmp;    Char *start;    Char *end;    if (!file | |!string) {return NULL;    }/* Open file */fd = open (file, o_rdonly);        if (FD < 0) {printf ("Open%s file error!\n", file);    return NULL; }/* Reads the file into the buffer */nread = read (fd, pbuf, sizeof (PBUF));//The contents of the file are stored in Pbuf if (Nread < 0) {printf ("Rea        D%s File error! ", file);    return NULL;    }/* Find the string in the file */ptmp = Strstr (Pbuf, String); Ptmp + = strlen (string);//skips the found string position while ((*ptmp = = ") | | (*ptmp = = ': ') | | (*pTMP = = ' \ t ')) ptmp++;    start = ptmp;    End = STRCHR (Ptmp, ");//Find the required data *end = ' + ';    memcpy (ResultStr, start, End-start); return resultstr;}    int main () {printf ("%s\n", Parse_string ("/proc/meminfo", "Memfree")); return 0;}

The contents of the C.txt file are as follows index1 = 45index2 = 36index3 = 231index4 = 43index5 = 100index6 = 123INDEX7 = 51
3. Read the C.txt file contents by reading the Equals right value, and print the right value maximum, minimum and average value to the screen.

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <    Errno.h>char *TRIMSTRR (char *srcstr)//Remove the space to the right of the string {if (srcstr = = null) return null;    int ilen = strlen (SRCSTR);    int i;        for (i = (iLen-1); I >= 0; i--) {if (srcstr[i] = = ") Srcstr[i] = 0;    else break; } return srcstr;}    Char *trimstrl (char *srcstr)//Remove the space at the left of the string {if (srcstr = = null) return null;    if (srcstr[0]! = ") return srcstr;    int ilen = strlen (SRCSTR);    if (Ilen = = 0) return srcstr;    Char *stmp = (char *) malloc (Ilen + 1);    memset (sTmp, 0, Ilen + 1);    memcpy (STMP, Srcstr, Ilen);    int i;            for (i = 0; i < Ilen; i++) {if (Srcstr[i]! = ") {strcpy (sTmp, srcstr + i);        Break    }} strcpy (Srcstr, STMP);    Free (STMP); return SRCSTR;} void Parsevaluestr (char *deststr, char *srcstr)//parse string with equals sign and remove word Nginx trailing space {intIlen = strlen (SRCSTR);    if (Ilen = = 0) return; if ((srcstr[ilen-1] = = ' \ n ') | | (srcstr[ilen-1] = = ' \ r '))    is compatible with the Windows format text file, so resolves the \ r character Srcstr[ilen-1] = ' + '; if (Ilen > 1) {if ((srcstr[ilen-2] = = ' \ n ') | | (Srcstr[ilen-2] = = ' \ r '))    is compatible with the Windows format text file, so resolves the \ r character Srcstr[ilen-2] = ' + '; } TRIMSTRR (SRCSTR);    Remove trailing space int i;            for (i = 0; i < Ilen; i++) {if ((*srcstr) = = ' = ') {strcpy (deststr, ++SRCSTR);        Break    } ++srcstr; } Trimstrl (DESTSTR);    Remove the header space}int max (const int *BUF, const int bufsize)//calculates the maximum value in the array buf, the parameter bufsize the number of elements buf the element {int tmp = buf[0];    int i = 0;    for (; i < bufsize; i++) {if (tmp <= buf[i]) tmp = Buf[i]; } return TMP;    int min (const int *BUF, const int bufsize)//calculates the minimum value in the array buf, and the parameter bufsize the number of elements buf the element {int tmp = buf[0];    int i = 0; for (; i < bufsize; i++) {if (tmp >= buf[i]) tmp =Buf[i]; } return TMP;    float AVG (const int *BUF, const int bufsize)//calculates the average value in the array buf, and the parameter bufsize the number of elements buf the element {float sum = 0;    int i = 0;    for (; i < bufsize; i++) {sum + = Buf[i]; } return sum/bufsize;}    int main (int arg, char *args[]) {const char *filename = "C.txt";    FILE *f = fopen (filename, "R");        if (f = = NULL)//file C.txt open error {printf ("Open%s failed%s\n", filename, strerror (errno));    return-1;    } Char svalue[100];    Char buf[100];    int ivalue[1024];    memset (ivalue, 0, sizeof (ivalue));    int i = 0; while (!) (        Feof (f)))//loop through each line of the file {memset (svalue, 0, sizeof (svalue));        memset (buf, 0, sizeof (BUF)); Fgets (svalue, sizeof (svalue), f); Reads a row of Parsevaluestr (buf, svalue) from the C.txt file;        Parse the string with equal sign and remove the word nginx trailing space ivalue[i] = atoi (BUF); i++;    Accumulator, which records the total number of rows in the C.txt file} fclose (f);    printf ("Maximum value is%d\n", Max (Ivalue, i));    printf ("Minimum value is%d\n", min (Ivalue, i));  printf ("Average value is%f\n", avg (Ivalue, i));  return 0;} 

Linux C Programming File Operation jobs